ClickHouse can accept and return data in various formats. A format supported for input can be used to parse the data provided to `INSERT`s, to perform `SELECT`s from a file-backed table such as File, URL or HDFS, or to read a dictionary. A format supported for output can be used to arrange the
You can control some format processing parameters with the ClickHouse settings. For more information read the [Settings](/docs/en/operations/settings/settings-formats.md) section.
In TabSeparated format, data is written by row. Each row contains values separated by tabs. Each value is followed by a tab, except the last value in the row, which is followed by a line feed. Strictly Unix line feeds are assumed everywhere. The last row also must contain a line feed at the end. Values are written in text format, without enclosing quotation marks, and with special characters escaped.
The `TabSeparated` format is convenient for processing data using custom programs and scripts. It is used by default in the HTTP interface, and in the command-line client’s batch mode. This format also allows transferring data between different DBMSs. For example, you can get a dump from MySQL and upload it to ClickHouse, or vice versa.
The `TabSeparated` format supports outputting total values (when using WITH TOTALS) and extreme values (when ‘extremes’ is set to 1). In these cases, the total values and extremes are output after the main data. The main result, total values, and extremes are separated from each other by an empty line. Example:
Integer numbers are written in decimal form. Numbers can contain an extra “+” character at the beginning (ignored when parsing, and not recorded when formatting). Non-negative numbers can’t contain the negative sign. When reading, it is allowed to parse an empty string as a zero, or (for signed types) a string consisting of just a minus sign as a zero. Numbers that do not fit into the corresponding data type may be parsed as a different number, without an error message.
Floating-point numbers are written in decimal form. The dot is used as the decimal separator. Exponential entries are supported, as are ‘inf’, ‘+inf’, ‘-inf’, and ‘nan’. An entry of floating-point numbers may begin or end with a decimal point.
Dates with times are written in the format `YYYY-MM-DD hh:mm:ss` and parsed in the same format, but with any characters as separators.
This all occurs in the system time zone at the time the client or server starts (depending on which of them formats data). For dates with times, daylight saving time is not specified. So if a dump has times during daylight saving time, the dump does not unequivocally match the data, and parsing will select one of the two times.
During a read operation, incorrect dates and dates with times can be parsed with natural overflow or as null dates and times, without an error message.
As an exception, parsing dates with times is also supported in Unix timestamp format, if it consists of exactly 10 decimal digits. The result is not time zone-dependent. The formats `YYYY-MM-DD hh:mm:ss` and `NNNNNNNNNN` are differentiated automatically.
Strings are output with backslash-escaped special characters. The following escape sequences are used for output: `\b`, `\f`, `\r`, `\n`, `\t`, `\0`, `\'`, `\\`. Parsing also supports the sequences `\a`, `\v`, and `\xHH` (hex escape sequences) and any `\c` sequences, where `c` is any character (these sequences are converted to `c`). Thus, reading data supports formats where a line feed can be written as `\n` or `\`, or as a line feed. For example, the string `Hello world` with a line feed between the words instead of space can be parsed in any of the following variations:
Arrays are written as a list of comma-separated values in square brackets. Number items in the array are formatted as normally. `Date` and `DateTime` types are written in single quotes. Strings are written in single quotes with the same escaping rules as above.
[NULL](/docs/en/sql-reference/syntax.md) is formatted according to setting [format_tsv_null_representation](/docs/en/operations/settings/settings-formats.md/#format_tsv_null_representation) (default value is `\N`).
In input data, ENUM values can be represented as names or as ids. First, we try to match the input value to the ENUM name. If we fail and the input value is a number, we try to match this number to ENUM id.
If input data contains only ENUM ids, it's recommended to enable the setting [input_format_tsv_enum_as_number](/docs/en/operations/settings/settings-formats.md/#input_format_tsv_enum_as_number) to optimize ENUM parsing.
- [format_tsv_null_representation](/docs/en/operations/settings/settings-formats.md/#format_tsv_null_representation) - custom NULL representation in TSV format. Default value - `\N`.
- [input_format_tsv_empty_as_default](/docs/en/operations/settings/settings-formats.md/#input_format_tsv_empty_as_default) - treat empty fields in TSV input as default values. Default value - `false`. For complex default expressions [input_format_defaults_for_omitted_fields](/docs/en/operations/settings/settings-formats.md/#input_format_defaults_for_omitted_fields) must be enabled too.
- [input_format_tsv_enum_as_number](/docs/en/operations/settings/settings-formats.md/#input_format_tsv_enum_as_number) - treat inserted enum values in TSV formats as enum indices. Default value - `false`.
- [input_format_tsv_use_best_effort_in_schema_inference](/docs/en/operations/settings/settings-formats.md/#input_format_tsv_use_best_effort_in_schema_inference) - use some tweaks and heuristics to infer schema in TSV format. If disabled, all fields will be inferred as Strings. Default value - `true`.
- [output_format_tsv_crlf_end_of_line](/docs/en/operations/settings/settings-formats.md/#output_format_tsv_crlf_end_of_line) - if it is set true, end of line in TSV output format will be `\r\n` instead of `\n`. Default value - `false`.
- [input_format_tsv_skip_first_lines](/docs/en/operations/settings/settings-formats.md/#input_format_tsv_skip_first_lines) - skip specified number of lines at the beginning of data. Default value - `0`.
- [input_format_tsv_detect_header](/docs/en/operations/settings/settings-formats.md/#input_format_tsv_detect_header) - automatically detect header with names and types in TSV format. Default value - `true`.
- [input_format_tsv_skip_trailing_empty_lines](/docs/en/operations/settings/settings-formats.md/#input_format_tsv_skip_trailing_empty_lines) - skip trailing empty lines at the end of data. Default value - `false`.
- [input_format_tsv_allow_variable_number_of_columns](/docs/en/operations/settings/settings-formats.md/#input_format_tsv_allow_variable_number_of_columns) - allow variable number of columns in TSV format, ignore extra columns and use default values on missing columns. Default value - `false`.
During parsing, the first row is expected to contain the column names. You can use column names to determine their position and to check their correctness.
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from the input data will be mapped to the columns of the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from the input data will be mapped to the columns in the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
It uses settings `format_template_resultset`, `format_template_row`, `format_template_rows_between_delimiter` and some settings of other formats (e.g.`output_format_json_quote_64bit_integers` when using `JSON` escaping, see further)
the values of `SearchPhrase`, `c` and `price` columns, which are escaped as `Quoted`, `Escaped` and `JSON` will be printed (for select) or will be expected (for insert) between `Search phrase:`, `, count:`, `, ad price: $` and `;` delimiters respectively. For example:
The `format_template_rows_between_delimiter` setting specifies the delimiter between rows, which is printed (or expected) after every row except the last one (`\n` by default)
Setting `format_template_resultset` specifies the path to the file, which contains a format string for resultset. Format string for resultset has the same syntax as a format string for row and allows to specify a prefix, a suffix and a way to print some additional information. It contains the following placeholders instead of column names:
-`data` is the rows with data in `format_template_row` format, separated by `format_template_rows_between_delimiter`. This placeholder must be the first placeholder in the format string.
-`totals` is the row with total values in `format_template_row` format (when using WITH TOTALS)
-`min` is the row with minimum values in `format_template_row` format (when extremes are set to 1)
-`max` is the row with maximum values in `format_template_row` format (when extremes are set to 1)
-`rows` is the total number of output rows
-`rows_before_limit` is the minimal number of rows there would have been without LIMIT. Output only if the query contains LIMIT. If the query contains GROUP BY, rows_before_limit_at_least is the exact number of rows there would have been without a LIMIT.
-`time` is the request execution time in seconds
-`rows_read` is the number of rows has been read
-`bytes_read` is the number of bytes (uncompressed) has been read
The placeholders `data`, `totals`, `min` and `max` must not have escaping rule specified (or `None` must be specified explicitly). The remaining placeholders may have any escaping rule specified.
`PageViews`, `UserID`, `Duration` and `Sign` inside placeholders are names of columns in the table. Values after `Useless field` in rows and after `\nTotal rows:` in suffix will be ignored.
Similar to `Template`, but skips whitespace characters between delimiters and values in the input stream. However, if format strings contain whitespace characters, these characters will be expected in the input stream. Also allows specifying empty placeholders (`${}` or `${:None}`) to split some delimiter into separate parts to ignore spaces between them. Such placeholders are used only for skipping whitespace characters.
It’s possible to read `JSON` using this format if the values of columns have the same order in all rows. For example, the following request can be used for inserting data from its output example of format [JSON](#json):
Similar to TabSeparated, but outputs a value in name=value format. Names are escaped the same way as in TabSeparated format, and the = symbol is also escaped.
When there is a large number of small columns, this format is ineffective, and there is generally no reason to use it. Nevertheless, it is no worse than JSONEachRow in terms of efficiency.
Both data output and parsing are supported in this format. For parsing, any order is supported for the values of different columns. It is acceptable for some values to be omitted – they are treated as equal to their default values. In this case, zeros and blank rows are used as default values. Complex values that could be specified in the table are not supported as defaults.
Parsing allows the presence of the additional field `tskv` without the equal sign or a value. This field is ignored.
During import, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
When formatting, rows are enclosed in double quotes. A double quote inside a string is output as two double quotes in a row. There are no other rules for escaping characters. Date and date-time are enclosed in double quotes. Numbers are output without quotes. Values are separated by a delimiter character, which is `,` by default. The delimiter character is defined in the setting [format_csv_delimiter](/docs/en/operations/settings/settings-formats.md/#format_csv_delimiter). Rows are separated using the Unix line feed (LF). Arrays are serialized in CSV as follows: first, the array is serialized to a string as in TabSeparated format, and then the resulting string is output to CSV in double quotes. Tuples in CSV format are serialized as separate columns (that is, their nesting in the tuple is lost).
\*By default, the delimiter is `,`. See the [format_csv_delimiter](/docs/en/operations/settings/settings-formats.md/#format_csv_delimiter) setting for more information.
When parsing, all values can be parsed either with or without quotes. Both double and single quotes are supported. Rows can also be arranged without quotes. In this case, they are parsed up to the delimiter character or line feed (CR or LF). In violation of the RFC, when parsing rows without quotes, the leading and trailing spaces and tabs are ignored. For the line feed, Unix (LF), Windows (CR LF) and Mac OS Classic (CR LF) types are all supported.
`NULL` is formatted according to setting [format_csv_null_representation](/docs/en/operations/settings/settings-formats.md/#format_csv_null_representation) (default value is `\N`).
In input data, ENUM values can be represented as names or as ids. First, we try to match the input value to the ENUM name. If we fail and the input value is a number, we try to match this number to the ENUM id.
If input data contains only ENUM ids, it's recommended to enable the setting [input_format_csv_enum_as_number](/docs/en/operations/settings/settings-formats.md/#input_format_csv_enum_as_number) to optimize ENUM parsing.
- [format_csv_delimiter](/docs/en/operations/settings/settings-formats.md/#format_csv_delimiter) - the character to be considered as a delimiter in CSV data. Default value - `,`.
- [format_csv_allow_single_quotes](/docs/en/operations/settings/settings-formats.md/#format_csv_allow_single_quotes) - allow strings in single quotes. Default value - `true`.
- [format_csv_allow_double_quotes](/docs/en/operations/settings/settings-formats.md/#format_csv_allow_double_quotes) - allow strings in double quotes. Default value - `true`.
- [format_csv_null_representation](/docs/en/operations/settings/settings-formats.md/#format_tsv_null_representation) - custom NULL representation in CSV format. Default value - `\N`.
- [input_format_csv_empty_as_default](/docs/en/operations/settings/settings-formats.md/#input_format_csv_empty_as_default) - treat empty fields in CSV input as default values. Default value - `true`. For complex default expressions, [input_format_defaults_for_omitted_fields](/docs/en/operations/settings/settings-formats.md/#input_format_defaults_for_omitted_fields) must be enabled too.
- [input_format_csv_enum_as_number](/docs/en/operations/settings/settings-formats.md/#input_format_csv_enum_as_number) - treat inserted enum values in CSV formats as enum indices. Default value - `false`.
- [input_format_csv_use_best_effort_in_schema_inference](/docs/en/operations/settings/settings-formats.md/#input_format_csv_use_best_effort_in_schema_inference) - use some tweaks and heuristics to infer schema in CSV format. If disabled, all fields will be inferred as Strings. Default value - `true`.
- [input_format_csv_arrays_as_nested_csv](/docs/en/operations/settings/settings-formats.md/#input_format_csv_arrays_as_nested_csv) - when reading Array from CSV, expect that its elements were serialized in nested CSV and then put into string. Default value - `false`.
- [output_format_csv_crlf_end_of_line](/docs/en/operations/settings/settings-formats.md/#output_format_csv_crlf_end_of_line) - if it is set to true, end of line in CSV output format will be `\r\n` instead of `\n`. Default value - `false`.
- [input_format_csv_skip_first_lines](/docs/en/operations/settings/settings-formats.md/#input_format_csv_skip_first_lines) - skip the specified number of lines at the beginning of data. Default value - `0`.
- [input_format_csv_detect_header](/docs/en/operations/settings/settings-formats.md/#input_format_csv_detect_header) - automatically detect header with names and types in CSV format. Default value - `true`.
- [input_format_csv_skip_trailing_empty_lines](/docs/en/operations/settings/settings-formats.md/#input_format_csv_skip_trailing_empty_lines) - skip trailing empty lines at the end of data. Default value - `false`.
- [input_format_csv_trim_whitespaces](/docs/en/operations/settings/settings-formats.md/#input_format_csv_trim_whitespaces) - trim spaces and tabs in non-quoted CSV strings. Default value - `true`.
- [input_format_csv_allow_whitespace_or_tab_as_delimiter](/docs/en/operations/settings/settings-formats.md/# input_format_csv_allow_whitespace_or_tab_as_delimiter) - Allow to use whitespace or tab as field delimiter in CSV strings. Default value - `false`.
- [input_format_csv_allow_variable_number_of_columns](/docs/en/operations/settings/settings-formats.md/#input_format_csv_allow_variable_number_of_columns) - allow variable number of columns in CSV format, ignore extra columns and use default values on missing columns. Default value - `false`.
- [input_format_csv_use_default_on_bad_values](/docs/en/operations/settings/settings-formats.md/#input_format_csv_use_default_on_bad_values) - Allow to set default value to column when CSV field deserialization failed on bad value. Default value - `false`.
- [input_format_csv_try_infer_numbers_from_strings](/docs/en/operations/settings/settings-formats.md/#input_format_csv_try_infer_numbers_from_strings) - Try to infer numbers from string fields while schema inference. Default value - `false`.
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
Similar to [Template](#format-template), but it prints or reads all names and types of columns and uses escaping rule from [format_custom_escaping_rule](/docs/en/operations/settings/settings-formats.md/#format_custom_escaping_rule) setting and delimiters from [format_custom_field_delimiter](/docs/en/operations/settings/settings-formats.md/#format_custom_field_delimiter), [format_custom_row_before_delimiter](/docs/en/operations/settings/settings-formats.md/#format_custom_row_before_delimiter), [format_custom_row_after_delimiter](/docs/en/operations/settings/settings-formats.md/#format_custom_row_after_delimiter), [format_custom_row_between_delimiter](/docs/en/operations/settings/settings-formats.md/#format_custom_row_between_delimiter), [format_custom_result_before_delimiter](/docs/en/operations/settings/settings-formats.md/#format_custom_result_before_delimiter) and [format_custom_result_after_delimiter](/docs/en/operations/settings/settings-formats.md/#format_custom_result_after_delimiter) settings, not from format strings.
- [input_format_custom_detect_header](/docs/en/operations/settings/settings-formats.md/#input_format_custom_detect_header) - enables automatic detection of header with names and types if any. Default value - `true`.
- [input_format_custom_skip_trailing_empty_lines](/docs/en/operations/settings/settings-formats.md/#input_format_custom_skip_trailing_empty_lines) - skip trailing empty lines at the end of file . Default value - `false`.
- [input_format_custom_allow_variable_number_of_columns](/docs/en/operations/settings/settings-formats.md/#input_format_custom_allow_variable_number_of_columns) - allow variable number of columns in CustomSeparated format, ignore extra columns and use default values on missing columns. Default value - `false`.
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
- [output_format_sql_insert_max_batch_size](/docs/en/operations/settings/settings-formats.md/#output_format_sql_insert_max_batch_size) - The maximum number of rows in one INSERT statement. Default value - `65505`.
- [output_format_sql_insert_table_name](/docs/en/operations/settings/settings-formats.md/#output_format_sql_insert_table_name) - The name of the table in the output INSERT query. Default value - `'table'`.
- [output_format_sql_insert_include_column_names](/docs/en/operations/settings/settings-formats.md/#output_format_sql_insert_include_column_names) - Include column names in INSERT query. Default value - `true`.
- [output_format_sql_insert_use_replace](/docs/en/operations/settings/settings-formats.md/#output_format_sql_insert_use_replace) - Use REPLACE statement instead of INSERT. Default value - `false`.
- [output_format_sql_insert_quote_names](/docs/en/operations/settings/settings-formats.md/#output_format_sql_insert_quote_names) - Quote column names with "\`" characters. Default value - `true`.
Outputs data in JSON format. Besides data tables, it also outputs column names and types, along with some additional information: the total number of output rows, and the number of rows that could have been output if there weren’t a LIMIT. Example:
The JSON is compatible with JavaScript. To ensure this, some characters are additionally escaped: the slash `/` is escaped as `\/`; alternative line breaks `U+2028` and `U+2029`, which break some browsers, are escaped as `\uXXXX`. ASCII control characters are escaped: backspace, form feed, line feed, carriage return, and horizontal tab are replaced with `\b`, `\f`, `\n`, `\r`, `\t` , as well as the remaining bytes in the 00-1F range using `\uXXXX` sequences. Invalid UTF-8 sequences are changed to the replacement character <20> so the output text will consist of valid UTF-8 sequences. For compatibility with JavaScript, Int64 and UInt64 integers are enclosed in double quotes by default. To remove the quotes, you can set the configuration parameter [output_format_json_quote_64bit_integers](/docs/en/operations/settings/settings-formats.md/#output_format_json_quote_64bit_integers) to 0.
ClickHouse supports [NULL](/docs/en/sql-reference/syntax.md), which is displayed as `null` in the JSON output. To enable `+nan`, `-nan`, `+inf`, `-inf` values in output, set the [output_format_json_quote_denormals](/docs/en/operations/settings/settings-formats.md/#output_format_json_quote_denormals) to 1.
For JSON input format, if setting [input_format_json_validate_types_from_metadata](/docs/en/operations/settings/settings-formats.md/#input_format_json_validate_types_from_metadata) is set to 1,
During import, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
Columns that are not present in the block will be filled with default values (you can use the [input_format_defaults_for_omitted_fields](/docs/en/operations/settings/settings-formats.md/#input_format_defaults_for_omitted_fields) setting here)
For JSONColumnsWithMetadata input format, if setting [input_format_json_validate_types_from_metadata](/docs/en/operations/settings/settings-formats.md/#input_format_json_validate_types_from_metadata) is set to 1,
In this format, a single JSON object is interpreted as a single value. If the input has several JSON objects (comma separated), they are interpreted as separate rows. If the input data is enclosed in square brackets, it is interpreted as an array of JSONs.
This format can only be parsed for a table with a single field of type [String](/docs/en/sql-reference/data-types/string.md). The remaining columns must be set to [DEFAULT](/docs/en/sql-reference/statements/create/table.md/#default) or [MATERIALIZED](/docs/en/sql-reference/statements/create/table.md/#materialized), or omitted. Once you collect the whole JSON object to string you can use [JSON functions](/docs/en/sql-reference/functions/json-functions.md) to process it.
Columns that are not present in the block will be filled with default values (you can use [input_format_defaults_for_omitted_fields](/docs/en/operations/settings/settings-formats.md/#input_format_defaults_for_omitted_fields) setting here)
While importing data columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
Differs from `JSONCompactEachRow` format in that it also prints the header row with column names, similar to [TabSeparatedWithNames](#tabseparatedwithnames).
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
Differs from `JSONCompactEachRow` format in that it also prints two header rows with column names and types, similar to [TabSeparatedWithNamesAndTypes](#tabseparatedwithnamesandtypes).
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
Differs from `JSONCompactStringsEachRow` in that in that it also prints the header row with column names, similar to [TabSeparatedWithNames](#tabseparatedwithnames).
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
Differs from `JSONCompactStringsEachRow` in that it also prints two header rows with column names and types, similar to [TabSeparatedWithNamesAndTypes](#tabseparatedwithnamesandtypes).
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
In this format, all data is represented as a single JSON Object, each row is represented as a separate field of this object similar to JSONEachRow format.
To use an object name as a column value you can use the special setting [format_json_object_each_row_column_for_object_name](/docs/en/operations/settings/settings-formats.md/#format_json_object_each_row_column_for_object_name). The value of this setting is set to the name of a column, that is used as JSON key for a row in the resulting object.
INSERT INTO UserActivity FORMAT JSONEachRow {"PageViews":5, "UserID":"4324182021466249494", "Duration":146,"Sign":-1} {"UserID":"4324182021466249494","PageViews":6,"Duration":185,"Sign":1}
ClickHouse ignores spaces between elements and commas after the objects. You can pass all the objects in one line. You do not have to separate them with line breaks.
If `DEFAULT expr` is specified, ClickHouse uses different substitution rules depending on the [input_format_defaults_for_omitted_fields](/docs/en/operations/settings/settings-formats.md/#input_format_defaults_for_omitted_fields) setting.
- If `input_format_defaults_for_omitted_fields = 0`, then the default value for `x` and `a` equals `0` (as the default value for the `UInt32` data type).
- If `input_format_defaults_for_omitted_fields = 1`, then the default value for `x` equals `0`, but the default value of `a` equals `x * 2`.
When inserting data with `input_format_defaults_for_omitted_fields = 1`, ClickHouse consumes more computational resources, compared to insertion with `input_format_defaults_for_omitted_fields = 0`.
Any set of bytes can be output in the strings. Use the `JSONEachRow` format if you are sure that the data in the table can be formatted as JSON without losing any information.
If you have a table with [Nested](/docs/en/sql-reference/data-types/nested-data-structures/index.md) data type columns, you can insert JSON data with the same structure. Enable this feature with the [input_format_import_nested_json](/docs/en/operations/settings/settings-formats.md/#input_format_import_nested_json) setting.
As you can see in the `Nested` data type description, ClickHouse treats each component of the nested structure as a separate column (`n.s` and `n.i` for our table). You can insert data in the following way:
To insert data as a hierarchical JSON object, set [input_format_import_nested_json=1](/docs/en/operations/settings/settings-formats.md/#input_format_import_nested_json).
- [input_format_import_nested_json](/docs/en/operations/settings/settings-formats.md/#input_format_import_nested_json) - map nested JSON data to nested tables (it works for JSONEachRow format). Default value - `false`.
- [input_format_json_read_bools_as_numbers](/docs/en/operations/settings/settings-formats.md/#input_format_json_read_bools_as_numbers) - allow to parse bools as numbers in JSON input formats. Default value - `true`.
- [input_format_json_read_numbers_as_strings](/docs/en/operations/settings/settings-formats.md/#input_format_json_read_numbers_as_strings) - allow to parse numbers as strings in JSON input formats. Default value - `true`.
- [input_format_json_read_arrays_as_strings](/docs/en/operations/settings/settings-formats.md/#input_format_json_read_arrays_as_strings) - allow to parse JSON arrays as strings in JSON input formats. Default value - `true`.
- [input_format_json_read_objects_as_strings](/docs/en/operations/settings/settings-formats.md/#input_format_json_read_objects_as_strings) - allow to parse JSON objects as strings in JSON input formats. Default value - `true`.
- [input_format_json_named_tuples_as_objects](/docs/en/operations/settings/settings-formats.md/#input_format_json_named_tuples_as_objects) - parse named tuple columns as JSON objects. Default value - `true`.
- [input_format_json_try_infer_numbers_from_strings](/docs/en/operations/settings/settings-formats.md/#input_format_json_try_infer_numbers_from_strings) - Try to infer numbers from string fields while schema inference. Default value - `false`.
- [input_format_json_try_infer_named_tuples_from_objects](/docs/en/operations/settings/settings-formats.md/#input_format_json_try_infer_named_tuples_from_objects) - try to infer named tuple from JSON objects during schema inference. Default value - `true`.
- [input_format_json_infer_incomplete_types_as_strings](/docs/en/operations/settings/settings-formats.md/#input_format_json_infer_incomplete_types_as_strings) - use type String for keys that contains only Nulls or empty objects/arrays during schema inference in JSON input formats. Default value - `true`.
- [input_format_json_defaults_for_missing_elements_in_named_tuple](/docs/en/operations/settings/settings-formats.md/#input_format_json_defaults_for_missing_elements_in_named_tuple) - insert default values for missing elements in JSON object while parsing named tuple. Default value - `true`.
- [input_format_json_ignore_unknown_keys_in_named_tuple](/docs/en/operations/settings/settings-formats.md/#input_format_json_ignore_unknown_keys_in_named_tuple) - Ignore unknown keys in json object for named tuples. Default value - `false`.
- [input_format_json_compact_allow_variable_number_of_columns](/docs/en/operations/settings/settings-formats.md/#input_format_json_compact_allow_variable_number_of_columns) - allow variable number of columns in JSONCompact/JSONCompactEachRow format, ignore extra columns and use default values on missing columns. Default value - `false`.
- [output_format_json_quote_64bit_integers](/docs/en/operations/settings/settings-formats.md/#output_format_json_quote_64bit_integers) - controls quoting of 64-bit integers in JSON output format. Default value - `true`.
- [output_format_json_quote_64bit_floats](/docs/en/operations/settings/settings-formats.md/#output_format_json_quote_64bit_floats) - controls quoting of 64-bit floats in JSON output format. Default value - `false`.
- [output_format_json_quote_denormals](/docs/en/operations/settings/settings-formats.md/#output_format_json_quote_denormals) - enables '+nan', '-nan', '+inf', '-inf' outputs in JSON output format. Default value - `false`.
- [output_format_json_quote_decimals](/docs/en/operations/settings/settings-formats.md/#output_format_json_quote_decimals) - controls quoting of decimals in JSON output format. Default value - `false`.
- [output_format_json_escape_forward_slashes](/docs/en/operations/settings/settings-formats.md/#output_format_json_escape_forward_slashes) - controls escaping forward slashes for string outputs in JSON output format. Default value - `true`.
- [output_format_json_named_tuples_as_objects](/docs/en/operations/settings/settings-formats.md/#output_format_json_named_tuples_as_objects) - serialize named tuple columns as JSON objects. Default value - `true`.
- [output_format_json_array_of_rows](/docs/en/operations/settings/settings-formats.md/#output_format_json_array_of_rows) - output a JSON array of all rows in JSONEachRow(Compact) format. Default value - `false`.
- [output_format_json_validate_utf8](/docs/en/operations/settings/settings-formats.md/#output_format_json_validate_utf8) - enables validation of UTF-8 sequences in JSON output formats (note that it doesn't impact formats JSON/JSONCompact/JSONColumnsWithMetadata, they always validate utf8). Default value - `false`.
Other BSON types are not supported. Also, it performs conversion between different integer types (for example, you can insert BSON int32 value into ClickHouse UInt8).
Big integers and decimals (Int128/UInt128/Int256/UInt256/Decimal128/Decimal256) can be parsed from BSON Binary value with `\x00` binary subtype. In this case this format will validate that the size of binary data equals the size of expected value.
- [output_format_bson_string_as_string](/docs/en/operations/settings/settings-formats.md/#output_format_bson_string_as_string) - use BSON String type instead of Binary for String columns. Default value - `false`.
- [input_format_bson_skip_fields_with_unsupported_types_in_schema_inference](/docs/en/operations/settings/settings-formats.md/#input_format_bson_skip_fields_with_unsupported_types_in_schema_inference) - allow skipping columns with unsupported types while schema inference for format BSONEachRow. Default value - `false`.
The most efficient format. Data is written and read by blocks in binary format. For each block, the number of rows, number of columns, column names and types, and parts of columns in this block are recorded one after another. In other words, this format is “columnar” – it does not convert columns to rows. This is the format used in the native interface for interaction between servers, for using the command-line client, and for C++ clients.
You can use this format to quickly generate dumps that can only be read by the ClickHouse DBMS. It does not make sense to work with this format yourself.
Nothing is output. However, the query is processed, and when using the command-line client, data is transmitted to the client. This is used for tests, including performance testing.
A full grid of the table is drawn, and each row occupies two lines in the terminal.
Each result block is output as a separate table. This is necessary so that blocks can be output without buffering results (buffering would be necessary in order to pre-calculate the visible width of all the values).
To avoid dumping too much data to the terminal, only the first 10,000 rows are printed. If the number of rows is greater than or equal to 10,000, the message “Showed first 10 000” is printed.
The Pretty format supports outputting total values (when using WITH TOTALS) and extremes (when ‘extremes’ is set to 1). In these cases, total values and extreme values are output after the main data, in separate tables. Example (shown for the [PrettyCompact](#prettycompact) format):
Differs from [Pretty](#pretty) in that ANSI-escape sequences aren’t used. This is necessary for displaying this format in a browser, as well as for using the ‘watch’ command-line utility.
Differs from [Pretty](#pretty) in that the grid is drawn between rows and the result is more compact.
This format is used by default in the command-line client in interactive mode.
## PrettyCompactNoEscapes {#prettynoescapes}
Differs from [PrettyCompact](#prettycompact) in that ANSI-escape sequences aren’t used. This is necessary for displaying this format in a browser, as well as for using the ‘watch’ command-line utility.
Differs from [PrettySpace](#prettyspace) in that ANSI-escape sequences aren’t used. This is necessary for displaying this format in a browser, as well as for using the ‘watch’ command-line utility.
## PrettySpaceMonoBlock {#prettyspacemonoblock}
Differs from [PrettySpace](#prettyspace) in that up to 10,000 rows are buffered, then output as a single table, not by blocks.
- [output_format_pretty_max_rows](/docs/en/operations/settings/settings-formats.md/#output_format_pretty_max_rows) - rows limit for Pretty formats. Default value - `10000`.
- [output_format_pretty_max_column_pad_width](/docs/en/operations/settings/settings-formats.md/#output_format_pretty_max_column_pad_width) - maximum width to pad all values in a column in Pretty formats. Default value - `250`.
- [output_format_pretty_max_value_width](/docs/en/operations/settings/settings-formats.md/#output_format_pretty_max_value_width) - Maximum width of value to display in Pretty formats. If greater - it will be cut. Default value - `10000`.
- [output_format_pretty_color](/docs/en/operations/settings/settings-formats.md/#output_format_pretty_color) - use ANSI escape sequences to paint colors in Pretty formats. Default value - `true`.
- [output_format_pretty_grid_charset](/docs/en/operations/settings/settings-formats.md/#output_format_pretty_grid_charset) - Charset for printing grid borders. Available charsets: ASCII, UTF-8. Default value - `UTF-8`.
- [output_format_pretty_row_numbers](/docs/en/operations/settings/settings-formats.md/#output_format_pretty_row_numbers) - Add row numbers before each row for pretty output format. Default value - `false`.
Formats and parses data by row in binary format. Rows and values are listed consecutively, without separators. Because data is in the binary format the delimiter after `FORMAT RowBinary` is strictly specified as next: any number of whitespaces (`' '` - space, code `0x20`; `'\t'` - tab, code `0x09`; `'\f'` - form feed, code `0x0C`) followed by exactly one new line sequence (Windows style `"\r\n"` or Unix style `'\n'`), immediately followed by binary data.
For [NULL](/docs/en/sql-reference/syntax.md/#null-literal) support, an additional byte containing 1 or 0 is added before each [Nullable](/docs/en/sql-reference/data-types/nullable.md) value. If 1, then the value is `NULL` and this byte is interpreted as a separate value. If 0, the value after the byte is not `NULL`.
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
If setting [input_format_with_names_use_header](/docs/en/operations/settings/settings-formats.md/#input_format_with_names_use_header) is set to 1,
the columns from input data will be mapped to the columns from the table by their names, columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
- [format_binary_max_string_size](/docs/en/operations/settings/settings-formats.md/#format_binary_max_string_size) - The maximum allowed size for String in RowBinary format. Default value - `1GiB`.
Prints every row in brackets. Rows are separated by commas. There is no comma after the last row. The values inside the brackets are also comma-separated. Numbers are output in a decimal format without quotes. Arrays are output in square brackets. Strings, dates, and dates with times are output in quotes. Escaping rules and parsing are similar to the [TabSeparated](#tabseparated) format. During formatting, extra spaces aren’t inserted, but during parsing, they are allowed and skipped (except for spaces inside array values, which are not allowed). [NULL](/docs/en/sql-reference/syntax.md) is represented as `NULL`.
- [input_format_values_interpret_expressions](/docs/en/operations/settings/settings-formats.md/#input_format_values_interpret_expressions) - if the field could not be parsed by streaming parser, run SQL parser and try to interpret it as SQL expression. Default value - `true`.
- [input_format_values_deduce_templates_of_expressions](/docs/en/operations/settings/settings-formats.md/#input_format_values_deduce_templates_of_expressions) -if the field could not be parsed by streaming parser, run SQL parser, deduce template of the SQL expression, try to parse all rows using template and then interpret expression for all rows. Default value - `true`.
- [input_format_values_accurate_types_of_literals](/docs/en/operations/settings/settings-formats.md/#input_format_values_accurate_types_of_literals) - when parsing and interpreting expressions using template, check actual type of literal to avoid possible overflow and precision issues. Default value - `true`.
Prints each value on a separate line with the column name specified. This format is convenient for printing just one or a few rows if each row consists of a large number of columns.
If the column name does not have an acceptable format, just ‘field’ is used as the element name. In general, the XML structure follows the JSON structure.
CapnProto is a binary message format similar to [Protocol Buffers](https://developers.google.com/protocol-buffers/) and [Thrift](https://en.wikipedia.org/wiki/Apache_Thrift), but not like [JSON](#json) or [MessagePack](https://msgpack.org/).
CapnProto messages are strictly typed and not self-describing, meaning they need an external schema description. The schema is applied on the fly and cached for each query.
See also [Format Schema](#formatschema).
### Data Types Matching {#data_types-matching-capnproto}
The table below shows supported data types and how they match ClickHouse [data types](/docs/en/sql-reference/data-types/index.md) in `INSERT` and `SELECT` queries.
For working with `Enum` in CapnProto format use the [format_capn_proto_enum_comparising_mode](/docs/en/operations/settings/settings-formats.md/#format_capn_proto_enum_comparising_mode) setting.
SELECT * FROM test.hits format CapnProto SETTINGS format_capn_proto_use_autogenerated_schema=1
```
In this case ClickHouse will autogenerate CapnProto schema according to the table structure using function [structureToCapnProtoSchema](../sql-reference/functions/other-functions.md#structure_to_capn_proto_schema) and will use this schema to serialize data in CapnProto format.
You can also read CapnProto file with autogenerated schema (in this case the file must be created using the same schema):
```bash
$ cat hits.bin | clickhouse-client --query "INSERT INTO test.hits SETTINGS format_capn_proto_use_autogenerated_schema=1 FORMAT CapnProto"
```
The setting [format_capn_proto_use_autogenerated_schema](../operations/settings/settings-formats.md#format_capn_proto_use_autogenerated_schema) is enabled by default and applies if [format_schema](../operations/settings/settings-formats.md#formatschema-format-schema) is not set.
You can also save autogenerated schema in the file during input/output using setting [output_format_schema](../operations/settings/settings-formats.md#outputformatschema-output-format-schema). For example:
```sql
SELECT * FROM test.hits format CapnProto SETTINGS format_capn_proto_use_autogenerated_schema=1, output_format_schema='path/to/schema/schema.capnp'
```
In this case autogenerated CapnProto schema will be saved in file `path/to/schema/schema.capnp`.
There's special requirements for labels for `histogram` and `summary`, see [Prometheus doc](https://prometheus.io/docs/instrumenting/exposition_formats/#histograms-and-summaries) for the details. Special rules applied to row with labels `{'count':''}` and `{'sum':''}`, they'll be converted to `<metric_name>_count` and `<metric_name>_sum` respectively.
ClickHouse inputs and outputs protobuf messages in the `length-delimited` format.
It means before every message should be written its length as a [varint](https://developers.google.com/protocol-buffers/docs/encoding#varints).
See also [how to read/write length-delimited protobuf messages in popular languages](https://cwiki.apache.org/confluence/display/GEODE/Delimiting+Protobuf+Messages).
SELECT * FROM test.hits format Protobuf SETTINGS format_protobuf_use_autogenerated_schema=1
```
In this case ClickHouse will autogenerate Protobuf schema according to the table structure using function [structureToProtobufSchema](../sql-reference/functions/other-functions.md#structure_to_protobuf_schema) and will use this schema to serialize data in Protobuf format.
You can also read Protobuf file with autogenerated schema (in this case the file must be created using the same schema):
```bash
$ cat hits.bin | clickhouse-client --query "INSERT INTO test.hits SETTINGS format_protobuf_use_autogenerated_schema=1 FORMAT Protobuf"
```
The setting [format_protobuf_use_autogenerated_schema](../operations/settings/settings-formats.md#format_protobuf_use_autogenerated_schema) is enabled by default and applies if [format_schema](../operations/settings/settings-formats.md#formatschema-format-schema) is not set.
You can also save autogenerated schema in the file during input/output using setting [output_format_schema](../operations/settings/settings-formats.md#outputformatschema-output-format-schema). For example:
```sql
SELECT * FROM test.hits format Protobuf SETTINGS format_protobuf_use_autogenerated_schema=1, output_format_schema='path/to/schema/schema.proto'
```
In this case autogenerated Protobuf schema will be saved in file `path/to/schema/schema.capnp`.
To reload Protobuf schema loaded from [format_schema_path](../operations/server-configuration-parameters/settings.md/#server_configuration_parameters-format_schema_path) use [SYSTEM DROP ... FORMAT CACHE](../sql-reference/statements/system.md/#system-drop-schema-format) statement.
The table below shows supported data types and how they match ClickHouse [data types](/docs/en/sql-reference/data-types/index.md) in `INSERT` and `SELECT` queries.
\* `bytes` is default, controlled by [output_format_avro_string_column_pattern](/docs/en/operations/settings/settings-formats.md/#output_format_avro_string_column_pattern)
Data types of ClickHouse table columns can differ from the corresponding fields of the Avro data inserted. When inserting data, ClickHouse interprets data types according to the table above and then [casts](/docs/en/sql-reference/functions/type-conversion-functions.md/#type_conversion_function-cast) the data to corresponding column type.
While importing data, when field is not found in schema and setting [input_format_avro_allow_missing_fields](/docs/en/operations/settings/settings-formats.md/#input_format_avro_allow_missing_fields) is enabled, default value will be used instead of error.
Output Avro file compression and sync interval can be configured with [output_format_avro_codec](/docs/en/operations/settings/settings-formats.md/#output_format_avro_codec) and [output_format_avro_sync_interval](/docs/en/operations/settings/settings-formats.md/#output_format_avro_sync_interval) respectively.
Using the ClickHouse [DESCRIBE](/docs/en/sql-reference/statements/describe-table) function, you can quickly view the inferred format of an Avro file like the following example. This example includes the URL of a publicly accessible Avro file in the ClickHouse S3 public bucket:
AvroConfluent supports decoding single-object Avro messages commonly used with [Kafka](https://kafka.apache.org/) and [Confluent Schema Registry](https://docs.confluent.io/current/schema-registry/index.html).
Each Avro message embeds a schema id that can be resolved to the actual schema with help of the Schema Registry.
Schema Registry URL is configured with [format_avro_schema_registry_url](/docs/en/operations/settings/settings-formats.md/#format_avro_schema_registry_url).
To quickly verify schema resolution you can use [kafkacat](https://github.com/edenhill/kafkacat) with [clickhouse-local](/docs/en/operations/utilities/clickhouse-local.md):
Setting `format_avro_schema_registry_url` needs to be configured in `users.xml` to maintain it’s value after a restart. Also you can use the `format_avro_schema_registry_url` setting of the `Kafka` table engine.
[Apache Parquet](https://parquet.apache.org/) is a columnar storage format widespread in the Hadoop ecosystem. ClickHouse supports read and write operations for this format.
The table below shows supported data types and how they match ClickHouse [data types](/docs/en/sql-reference/data-types/index.md) in `INSERT` and `SELECT` queries.
Data types of ClickHouse table columns can differ from the corresponding fields of the Parquet data inserted. When inserting data, ClickHouse interprets data types according to the table above and then [cast](/docs/en/sql-reference/functions/type-conversion-functions/#type_conversion_function-cast) the data to that data type which is set for the ClickHouse table column.
- [output_format_parquet_row_group_size](/docs/en/operations/settings/settings-formats.md/#output_format_parquet_row_group_size) - row group size in rows while data output. Default value - `1000000`.
- [output_format_parquet_string_as_string](/docs/en/operations/settings/settings-formats.md/#output_format_parquet_string_as_string) - use Parquet String type instead of Binary for String columns. Default value - `false`.
- [input_format_parquet_import_nested](/docs/en/operations/settings/settings-formats.md/#input_format_parquet_import_nested) - allow inserting array of structs into [Nested](/docs/en/sql-reference/data-types/nested-data-structures/index.md) table in Parquet input format. Default value - `false`.
- [input_format_parquet_case_insensitive_column_matching](/docs/en/operations/settings/settings-formats.md/#input_format_parquet_case_insensitive_column_matching) - ignore case when matching Parquet columns with ClickHouse columns. Default value - `false`.
- [input_format_parquet_allow_missing_columns](/docs/en/operations/settings/settings-formats.md/#input_format_parquet_allow_missing_columns) - allow missing columns while reading Parquet data. Default value - `false`.
- [input_format_parquet_skip_columns_with_unsupported_types_in_schema_inference](/docs/en/operations/settings/settings-formats.md/#input_format_parquet_skip_columns_with_unsupported_types_in_schema_inference) - allow skipping columns with unsupported types while schema inference for Parquet format. Default value - `false`.
- [input_format_parquet_local_file_min_bytes_for_seek](/docs/en/operations/settings/settings-formats.md/#input_format_parquet_local_file_min_bytes_for_seek) - min bytes required for local read (file) to do seek, instead of read with ignore in Parquet input format. Default value - `8192`.
- [output_format_parquet_fixed_string_as_fixed_byte_array](/docs/en/operations/settings/settings-formats.md/#output_format_parquet_fixed_string_as_fixed_byte_array) - use Parquet FIXED_LENGTH_BYTE_ARRAY type instead of Binary/String for FixedString columns. Default value - `true`.
- [output_format_parquet_version](/docs/en/operations/settings/settings-formats.md/#output_format_parquet_version) - The version of Parquet format used in output format. Default value - `2.latest`.
- [output_format_parquet_compression_method](/docs/en/operations/settings/settings-formats.md/#output_format_parquet_compression_method) - compression method used in output Parquet format. Default value - `lz4`.
Special format for reading Parquet file metadata (https://parquet.apache.org/docs/file-format/metadata/). It always outputs one row with the next structure/content:
- num_columns - the number of columns
- num_rows - the total number of rows
- num_row_groups - the total number of row groups
- format_version - parquet format version, always 1.0 or 2.6
- total_uncompressed_size - total uncompressed bytes size of the column, calculated as the sum of total_uncompressed_size of the column from all row groups
[Apache Arrow](https://arrow.apache.org/) comes with two built-in columnar storage formats. ClickHouse supports read and write operations for these formats.
The table below shows supported data types and how they match ClickHouse [data types](/docs/en/sql-reference/data-types/index.md) in `INSERT` and `SELECT` queries.
The `DICTIONARY` type is supported for `INSERT` queries, and for `SELECT` queries there is an [output_format_arrow_low_cardinality_as_dictionary](/docs/en/operations/settings/settings-formats.md/#output-format-arrow-low-cardinality-as-dictionary) setting that allows to output [LowCardinality](/docs/en/sql-reference/data-types/lowcardinality.md) type as a `DICTIONARY` type.
The data types of ClickHouse table columns do not have to match the corresponding Arrow data fields. When inserting data, ClickHouse interprets data types according to the table above and then [casts](/docs/en/sql-reference/functions/type-conversion-functions.md/#type_conversion_function-cast) the data to the data type set for the ClickHouse table column.
- [output_format_arrow_low_cardinality_as_dictionary](/docs/en/operations/settings/settings-formats.md/#output_format_arrow_low_cardinality_as_dictionary) - enable output ClickHouse LowCardinality type as Dictionary Arrow type. Default value - `false`.
- [output_format_arrow_string_as_string](/docs/en/operations/settings/settings-formats.md/#output_format_arrow_string_as_string) - use Arrow String type instead of Binary for String columns. Default value - `false`.
- [input_format_arrow_case_insensitive_column_matching](/docs/en/operations/settings/settings-formats.md/#input_format_arrow_case_insensitive_column_matching) - ignore case when matching Arrow columns with ClickHouse columns. Default value - `false`.
- [input_format_arrow_allow_missing_columns](/docs/en/operations/settings/settings-formats.md/#input_format_arrow_allow_missing_columns) - allow missing columns while reading Arrow data. Default value - `false`.
- [input_format_arrow_skip_columns_with_unsupported_types_in_schema_inference](/docs/en/operations/settings/settings-formats.md/#input_format_arrow_skip_columns_with_unsupported_types_in_schema_inference) - allow skipping columns with unsupported types while schema inference for Arrow format. Default value - `false`.
- [output_format_arrow_fixed_string_as_fixed_byte_array](/docs/en/operations/settings/settings-formats.md/#output_format_arrow_fixed_string_as_fixed_byte_array) - use Arrow FIXED_SIZE_BINARY type instead of Binary/String for FixedString columns. Default value - `true`.
- [output_format_arrow_compression_method](/docs/en/operations/settings/settings-formats.md/#output_format_arrow_compression_method) - compression method used in output Arrow format. Default value - `lz4_frame`.
The table below shows supported data types and how they match ClickHouse [data types](/docs/en/sql-reference/data-types/index.md) in `INSERT` and `SELECT` queries.
The data types of ClickHouse table columns do not have to match the corresponding ORC data fields. When inserting data, ClickHouse interprets data types according to the table above and then [casts](/docs/en/sql-reference/functions/type-conversion-functions.md/#type_conversion_function-cast) the data to the data type set for the ClickHouse table column.
- [output_format_arrow_string_as_string](/docs/en/operations/settings/settings-formats.md/#output_format_arrow_string_as_string) - use Arrow String type instead of Binary for String columns. Default value - `false`.
- [output_format_orc_compression_method](/docs/en/operations/settings/settings-formats.md/#output_format_orc_compression_method) - compression method used in output ORC format. Default value - `none`.
- [input_format_arrow_case_insensitive_column_matching](/docs/en/operations/settings/settings-formats.md/#input_format_arrow_case_insensitive_column_matching) - ignore case when matching Arrow columns with ClickHouse columns. Default value - `false`.
- [input_format_arrow_allow_missing_columns](/docs/en/operations/settings/settings-formats.md/#input_format_arrow_allow_missing_columns) - allow missing columns while reading Arrow data. Default value - `false`.
- [input_format_arrow_skip_columns_with_unsupported_types_in_schema_inference](/docs/en/operations/settings/settings-formats.md/#input_format_arrow_skip_columns_with_unsupported_types_in_schema_inference) - allow skipping columns with unsupported types while schema inference for Arrow format. Default value - `false`.
Special input format that doesn't read any data from file and returns only one row with column of type `UInt8`, name `dummy` and value `0` (like `system.one` table).
Can be used with virtual columns `_file/_path` to list all files without reading actual data.
Example:
Query:
```sql
SELECT _file FROM file('path/to/files/data*', One);
This function is designed to load a NumPy array from a .npy file into ClickHouse. The NumPy file format is a binary format used for efficiently storing arrays of numerical data. During import, ClickHouse treats top level dimension as an array of rows with single column. Supported Npy data types and their corresponding type in ClickHouse:
In this format, every line of input data is interpreted as a single string value. This format can only be parsed for table with a single field of type [String](/docs/en/sql-reference/data-types/string.md). The remaining columns must be set to [DEFAULT](/docs/en/sql-reference/statements/create/table.md/#default) or [MATERIALIZED](/docs/en/sql-reference/statements/create/table.md/#materialized), or omitted.
-`format_regexp` — [String](/docs/en/sql-reference/data-types/string.md). Contains regular expression in the [re2](https://github.com/google/re2/wiki/Syntax) format.
-`format_regexp_skip_unmatched` — [UInt8](/docs/en/sql-reference/data-types/int-uint.md). Defines the need to throw an exception in case the `format_regexp` expression does not match the imported data. Can be set to `0` or `1`.
The regular expression from [format_regexp](/docs/en/operations/settings/settings-formats.md/#format_regexp) setting is applied to every line of imported data. The number of subpatterns in the regular expression must be equal to the number of columns in imported dataset.
The content of every matched subpattern is parsed with the method of corresponding data type, according to [format_regexp_escaping_rule](/docs/en/operations/settings/settings-formats.md/#format_regexp_escaping_rule) setting.
If the regular expression does not match the line and [format_regexp_skip_unmatched](/docs/en/operations/settings/settings-formats.md/#format_regexp_escaping_rule) is set to 1, the line is silently skipped. Otherwise, exception is thrown.
If you input or output data via the [client](/docs/en/interfaces/cli.md) in the [interactive mode](/docs/en/interfaces/cli.md/#cli_usage), the file name specified in the format schema
If you input or output data via the [HTTP interface](/docs/en/interfaces/http.md) the file name specified in the format schema
should be located in the directory specified in [format_schema_path](/docs/en/operations/server-configuration-parameters/settings.md/#server_configuration_parameters-format_schema_path)
Some formats such as `CSV`, `TabSeparated`, `TSKV`, `JSONEachRow`, `Template`, `CustomSeparated` and `Protobuf` can skip broken row if parsing error occurred and continue parsing from the beginning of next row. See [input_format_allow_errors_num](/docs/en/operations/settings/settings-formats.md/#input_format_allow_errors_num) and
- In case of parsing error `JSONEachRow` skips all data until the new line (or EOF), so rows must be delimited by `\n` to count errors correctly.
-`Template` and `CustomSeparated` use delimiter after the last column and delimiter between rows to find the beginning of next row, so skipping errors works only if at least one of them is not empty.
In this format, all input data is read to a single value. It is possible to parse only a table with a single field of type [String](/docs/en/sql-reference/data-types/string.md) or similar.
The result is output in binary format without delimiters and escaping. If more than one value is output, the format is ambiguous, and it will be impossible to read the data back.
- String fields are represented as length in varint format (unsigned [LEB128] (https://en.wikipedia.org/wiki/LEB128)), followed by the bytes of the string.
- [input_format_msgpack_number_of_columns](/docs/en/operations/settings/settings-formats.md/#input_format_msgpack_number_of_columns) - the number of columns in inserted MsgPack data. Used for automatic schema inference from data. Default value - `0`.
- [output_format_msgpack_uuid_representation](/docs/en/operations/settings/settings-formats.md/#output_format_msgpack_uuid_representation) - the way how to output UUID in MsgPack format. Default value - `EXT`.
You can specify the name of the table from which to read data from using [input_format_mysql_dump_table_name](/docs/en/operations/settings/settings-formats.md/#input_format_mysql_dump_table_name) settings.
If setting [input_format_mysql_dump_map_columns](/docs/en/operations/settings/settings-formats.md/#input_format_mysql_dump_map_columns) is set to 1 and
dump contains CREATE query for specified table or column names in INSERT query the columns from input data will be mapped to the columns from the table by their names,
columns with unknown names will be skipped if setting [input_format_skip_unknown_fields](/docs/en/operations/settings/settings-formats.md/#input_format_skip_unknown_fields) is set to 1.
This format supports schema inference: if the dump contains CREATE query for the specified table, the structure is extracted from it, otherwise schema is inferred from the data of INSERT queries.
Examples:
File dump.sql:
```sql
/*!40101 SET @saved_cs_client = @@character_set_client */;
Parses DWARF debug symbols from an ELF file (executable, library, or object file). Similar to `dwarfdump`, but much faster (hundreds of MB/s) and with SQL. Produces one row for each Debug Information Entry (DIE) in the `.debug_info` section. Includes "null" entries that the DWARF encoding uses to terminate lists of children in the tree.
Quick background: `.debug_info` consists of *units*, corresponding to compilation units. Each unit is a tree of *DIE*s, with a `compile_unit` DIE as its root. Each DIE has a *tag* and a list of *attributes*. Each attribute has a *name* and a *value* (and also a *form*, which specifies how the value is encoded). The DIEs represent things from the source code, and their *tag* tells what kind of thing it is. E.g. there are functions (tag = `subprogram`), classes/structs/enums (`class_type`/`structure_type`/`enumeration_type`), variables (`variable`), function arguments (`formal_parameter`). The tree structure mirrors the corresponding source code. E.g. a `class_type` DIE can contain `subprogram` DIEs representing methods of the class.
Outputs the following columns:
-`offset` - position of the DIE in the `.debug_info` section
-`size` - number of bytes in the encoded DIE (including attributes)
-`tag` - type of the DIE; the conventional "DW_TAG_" prefix is omitted
-`unit_name` - name of the compilation unit containing this DIE
-`unit_offset` - position of the compilation unit containing this DIE in the `.debug_info` section
-`ancestor_tags` - array of tags of the ancestors of the current DIE in the tree, in order from innermost to outermost
-`ancestor_offsets` - offsets of ancestors, parallel to `ancestor_tags`
- a few common attributes duplicated from the attributes array for convenience:
-`name`
-`linkage_name` - mangled fully-qualified name; typically only functions have it (but not all functions)
-`decl_file` - name of the source code file where this entity was declared
-`decl_line` - line number in the source code where this entity was declared
- parallel arrays describing attributes:
-`attr_name` - name of the attribute; the conventional "DW_AT_" prefix is omitted
-`attr_form` - how the attribute is encoded and interpreted; the conventional DW_FORM_ prefix is omitted
-`attr_int` - integer value of the attribute; 0 if the attribute doesn't have a numeric value
-`attr_str` - string value of the attribute; empty if the attribute doesn't have a string value
Example: find compilation units that have the most function definitions (including template instantiations and functions from included header files):
```sql
SELECT
unit_name,
count() AS c
FROM file('programs/clickhouse', DWARF)
WHERE tag = 'subprogram' AND NOT has(attr_name, 'declaration')
