Enables or disables skipping insertion of extra data.
When writing data, ClickHouse throws an exception if input data contain columns that do not exist in the target table. If skipping is enabled, ClickHouse does not insert extra data and does not throw an exception.
Enables or disables checking the column order when inserting data.
To improve insert performance, we recommend disabling this check if you are sure that the column order of the input data is the same as in the target table.
When performing `INSERT` queries, replace omitted input column values with default values of the respective columns. This option applies to [JSONEachRow](../../interfaces/formats.md/#jsoneachrow) (and other JSON formats), [CSV](../../interfaces/formats.md/#csv), [TabSeparated](../../interfaces/formats.md/#tabseparated), [TSKV](../../interfaces/formats.md/#tskv), [Parquet](../../interfaces/formats.md/#parquet), [Arrow](../../interfaces/formats.md/#arrow), [Avro](../../interfaces/formats.md/#avro), [ORC](../../interfaces/formats.md/#orc), [Native](../../interfaces/formats.md/#native) formats and formats with `WithNames`/`WithNamesAndTypes` suffixes.
When this option is enabled, extended table metadata are sent from server to client. It consumes additional computing resources on the server and can reduce performance.
Enables or disables the initialization of [NULL](../../sql-reference/syntax.md/#null-literal) fields with [default values](../../sql-reference/statements/create/table.md/#create-default-values), if data type of these fields is not [nullable](../../sql-reference/data-types/nullable.md/#data_type-nullable).
If column type is not nullable and this setting is disabled, then inserting `NULL` causes an exception. If column type is nullable, then `NULL` values are inserted as is, regardless of this setting.
If the `schema_inference_hints` is not formated properly, or if there is a typo or a wrong datatype, etc... the whole schema_inference_hints will be ignored.
If enabled, ClickHouse will try to infer integers instead of floats in schema inference for text formats. If all numbers in the column from input data are integers, the result type will be `Int64`, if at least one number is float, the result type will be `Float64`.
If enabled, ClickHouse will try to infer type `Date` from string fields in schema inference for text formats. If all fields from a column in input data were successfully parsed as dates, the result type will be `Date`, if at least one field was not parsed as date, the result type will be `String`.
If enabled, ClickHouse will try to infer type `DateTime64` from string fields in schema inference for text formats. If all fields from a column in input data were successfully parsed as datetimes, the result type will be `DateTime64`, if at least one field was not parsed as datetime, the result type will be `String`.
Allows choosing a parser of the text representation of date and time.
The setting does not apply to [date and time functions](../../sql-reference/functions/date-time-functions.md).
Possible values:
-`'best_effort'` — Enables extended parsing.
ClickHouse can parse the basic `YYYY-MM-DD HH:MM:SS` format and all [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601) date and time formats. For example, `'2018-06-08T01:02:03.000Z'`.
-`'basic'` — Use basic parser.
ClickHouse can parse only the basic `YYYY-MM-DD HH:MM:SS` or `YYYY-MM-DD` format. For example, `2019-08-20 10:18:56` or `2019-08-20`.
Default value: `'basic'`.
See also:
- [DateTime data type.](../../sql-reference/data-types/datetime.md)
- [Functions for working with dates and times.](../../sql-reference/functions/date-time-functions.md)
Allows choosing different output formats of the text representation of date and time.
Possible values:
-`simple` - Simple output format.
ClickHouse output date and time `YYYY-MM-DD hh:mm:ss` format. For example, `2019-08-20 10:18:56`. The calculation is performed according to the data type's time zone (if present) or server time zone.
-`iso` - ISO output format.
ClickHouse output date and time in [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601) `YYYY-MM-DDThh:mm:ssZ` format. For example, `2019-08-20T10:18:56Z`. Note that output is in UTC (`Z` means UTC).
-`unix_timestamp` - Unix timestamp output format.
ClickHouse output date and time in [Unix timestamp](https://en.wikipedia.org/wiki/Unix_time) format. For example `1566285536`.
Default value: `simple`.
See also:
- [DateTime data type.](../../sql-reference/data-types/datetime.md)
- [Functions for working with dates and times.](../../sql-reference/functions/date-time-functions.md)
Sets the maximum number of acceptable errors when reading from text formats (CSV, TSV, etc.).
The default value is 0.
Always pair it with `input_format_allow_errors_ratio`.
If an error occurred while reading rows but the error counter is still less than `input_format_allow_errors_num`, ClickHouse ignores the row and moves on to the next one.
If both `input_format_allow_errors_num` and `input_format_allow_errors_ratio` are exceeded, ClickHouse throws an exception.
Sets the maximum percentage of errors allowed when reading from text formats (CSV, TSV, etc.).
The percentage of errors is set as a floating-point number between 0 and 1.
The default value is 0.
Always pair it with `input_format_allow_errors_num`.
If an error occurred while reading rows but the error counter is still less than `input_format_allow_errors_ratio`, ClickHouse ignores the row and moves on to the next one.
If both `input_format_allow_errors_num` and `input_format_allow_errors_ratio` are exceeded, ClickHouse throws an exception.
## format_schema {#format-schema}
This parameter is useful when you are using formats that require a schema definition, such as [Cap’n Proto](https://capnproto.org/) or [Protobuf](https://developers.google.com/protocol-buffers/). The value depends on the format.
Enables or disables random shard insertion into a [Distributed](../../engines/table-engines/special/distributed.md/#distributed) table when there is no distributed key.
By default, when inserting data into a `Distributed` table with more than one shard, the ClickHouse server will reject any insertion request if there is no distributed key. When `insert_distributed_one_random_shard = 1`, insertions are allowed and data is forwarded randomly among all shards.
Possible values:
- 0 — Insertion is rejected if there are multiple shards and no distributed key is given.
- 1 — Insertion is done randomly among all available shards when no distributed key is given.
Controls quoting of 64-bit or bigger [integers](../../sql-reference/data-types/int-uint.md) (like `UInt64` or `Int128`) when they are output in a [JSON](../../interfaces/formats.md/#json) format.
Such integers are enclosed in quotes by default. This behavior is compatible with most JavaScript implementations.
Controls escaping forward slashes for string outputs in JSON output format. This is intended for compatibility with JavaScript. Don't confuse with backslashes that are always escaped.
When enabled, replace empty input fields in TSV with default values. For complex default expressions `input_format_defaults_for_omitted_fields` must be enabled too.
When enabled, always treat enum values as enum ids for TSV input format. It's recommended to enable this setting if data contains only enum ids to optimize enum parsing.
Possible values:
- 0 — Enum values are parsed as values or as enum IDs.
Defines the representation of `NULL` for [TSV](../../interfaces/formats.md/#tabseparated) output and input formats. User can set any string as a value, for example, `My NULL`.
Default value: `\N`.
**Examples**
Query
```sql
SELECT * FROM tsv_custom_null FORMAT TSV;
```
Result
```text
788
\N
\N
```
Query
```sql
SET format_tsv_null_representation = 'My NULL';
SELECT * FROM tsv_custom_null FORMAT TSV;
```
Result
```text
788
My NULL
My NULL
```
## CSV format settings {#csv-format-settings}
### format_csv_delimiter {#format_csv_delimiter}
The character is interpreted as a delimiter in the CSV data.
When enabled, always treat enum values as enum ids for CSV input format. It's recommended to enable this setting if data contains only enum ids to optimize enum parsing.
Possible values:
- 0 — Enum values are parsed as values or as enum IDs.
When reading Array from CSV, expect that its elements were serialized in nested CSV and then put into string. Example: "[""Hello"", ""world"", ""42"""" TV""]". Braces around array can be omitted.
When enabled, replace empty input fields in CSV with default values. For complex default expressions `input_format_defaults_for_omitted_fields` must be enabled too.
Defines the representation of `NULL` for [CSV](../../interfaces/formats.md/#csv) output and input formats. User can set any string as a value, for example, `My NULL`.
Default value: `\N`.
**Examples**
Query
```sql
SELECT * from csv_custom_null FORMAT CSV;
```
Result
```text
788
\N
\N
```
Query
```sql
SET format_csv_null_representation = 'My NULL';
SELECT * FROM csv_custom_null FORMAT CSV;
```
Result
```text
788
My NULL
My NULL
```
## Values format settings {#values-format-settings}
Enables or disables the full SQL parser if the fast stream parser can’t parse the data. This setting is used only for the [Values](../../interfaces/formats.md/#data-format-values) format at the data insertion. For more information about syntax parsing, see the [Syntax](../../sql-reference/syntax.md) section.
Possible values:
- 0 — Disabled.
In this case, you must provide formatted data. See the [Formats](../../interfaces/formats.md) section.
- 1 — Enabled.
In this case, you can use an SQL expression as a value, but data insertion is much slower this way. If you insert only formatted data, then ClickHouse behaves as if the setting value is 0.
Default value: 1.
Example of Use
Insert the [DateTime](../../sql-reference/data-types/datetime.md) type value with the different settings.
``` sql
SET input_format_values_interpret_expressions = 0;
Enables or disables template deduction for SQL expressions in [Values](../../interfaces/formats.md/#data-format-values) format. It allows parsing and interpreting expressions in `Values` much faster if expressions in consecutive rows have the same structure. ClickHouse tries to deduce the template of an expression, parse the following rows using this template and evaluate the expression on a batch of successfully parsed rows.
Possible values:
- 0 — Disabled.
- 1 — Enabled.
Default value: 1.
For the following query:
``` sql
INSERT INTO test VALUES (lower('Hello')), (lower('world')), (lower('INSERT')), (upper('Values')), ...
```
- If `input_format_values_interpret_expressions=1` and `format_values_deduce_templates_of_expressions=0`, expressions are interpreted separately for each row (this is very slow for large number of rows).
- If `input_format_values_interpret_expressions=0` and `format_values_deduce_templates_of_expressions=1`, expressions in the first, second and third rows are parsed using template `lower(String)` and interpreted together, expression in the forth row is parsed with another template (`upper(String)`).
- If `input_format_values_interpret_expressions=1` and `format_values_deduce_templates_of_expressions=1`, the same as in previous case, but also allows fallback to interpreting expressions separately if it’s not possible to deduce template.
This setting is used only when `input_format_values_deduce_templates_of_expressions = 1`. Expressions for some column may have the same structure, but contain numeric literals of different types, e.g.
``` sql
(..., abs(0), ...), -- UInt64 literal
(..., abs(3.141592654), ...), -- Float64 literal
(..., abs(-1), ...), -- Int64 literal
```
Possible values:
- 0 — Disabled.
In this case, ClickHouse may use a more general type for some literals (e.g.,`Float64` or `Int64` instead of `UInt64` for `42`), but it may cause overflow and precision issues.
- 1 — Enabled.
In this case, ClickHouse checks the actual type of literal and uses an expression template of the corresponding type. In some cases, it may significantly slow down expression evaluation in `Values`.
Enables or disables the ability to insert the data into [Nested](../../sql-reference/data-types/nested-data-structures/index.md) columns as an array of structs in [Arrow](../../interfaces/formats.md/#data_types-matching-arrow) input format.
Allows to convert the [LowCardinality](../../sql-reference/data-types/lowcardinality.md) type to the `DICTIONARY` type of the [Arrow](../../interfaces/formats.md/#data-format-arrow) format for `SELECT` queries.
Possible values:
- 0 — The `LowCardinality` type is not converted to the `DICTIONARY` type.
- 1 — The `LowCardinality` type is converted to the `DICTIONARY` type.
Enables or disables the ability to insert the data into [Nested](../../sql-reference/data-types/nested-data-structures/index.md) columns as an array of structs in [ORC](../../interfaces/formats.md/#data-format-orc) input format.
Enables or disables the ability to insert the data into [Nested](../../sql-reference/data-types/nested-data-structures/index.md) columns as an array of structs in [Parquet](../../interfaces/formats.md/#data-format-parquet) input format.
Enable Google wrappers for regular non-nested columns, e.g. google.protobuf.StringValue 'str' for String column 'str'. For Nullable columns empty wrappers are recognized as defaults, and missing as nulls.
When serializing Nullable columns with Google wrappers, serialize default values as empty wrappers. If turned off, default and null values are not serialized.
Enables using fields that are not specified in [Avro](../../interfaces/formats.md/#data-format-avro) or [AvroConfluent](../../interfaces/formats.md/#data-format-avro-confluent) format schema. When a field is not found in the schema, ClickHouse uses the default value instead of throwing an exception.
Sets [Confluent Schema Registry](https://docs.confluent.io/current/schema-registry/index.html) URL to use with [AvroConfluent](../../interfaces/formats.md/#data-format-avro-confluent) format.
Sets the character that is interpreted as a delimiter between the fields for [CustomSeparated](../../interfaces/formats.md/#format-customseparated) data format.
Sets the character that is interpreted as a delimiter before the field of the first column for [CustomSeparated](../../interfaces/formats.md/#format-customseparated) data format.
Sets the character that is interpreted as a delimiter after the field of the last column for [CustomSeparated](../../interfaces/formats.md/#format-customseparated) data format.
Sets the character that is interpreted as a delimiter between the rows for [CustomSeparated](../../interfaces/formats.md/#format-customseparated) data format.
Sets the character that is interpreted as a prefix before the result set for [CustomSeparated](../../interfaces/formats.md/#format-customseparated) data format.
Sets the character that is interpreted as a suffix after the result set for [CustomSeparated](../../interfaces/formats.md/#format-customseparated) data format.
Default value: `''`.
## Regexp format settings {#regexp-format-settings}
The maximum allowed size for String in RowBinary format. It prevents allocating large amount of memory in case of corrupted data. 0 means there is no limit.
