4.8 KiB
slug | sidebar_position | sidebar_label |
---|---|---|
/en/sql-reference/table-functions/file | 37 | file |
file
Creates a table from a file. This table function is similar to url and hdfs ones.
file
function can be used in SELECT
and INSERT
queries on data in File tables.
Syntax
file(path [,format] [,structure])
Parameters
path
— The relative path to the file from user_files_path. Path to file support following globs in read-only mode:*
,?
,{abc,def}
and{N..M}
whereN
,M
— numbers,'abc', 'def'
— strings.format
— The format of the file.structure
— Structure of the table. Format:'column1_name column1_type, column2_name column2_type, ...'
.
Returned value
A table with the specified structure for reading or writing data in the specified file.
Examples
Setting user_files_path
and the contents of the file test.csv
:
$ grep user_files_path /etc/clickhouse-server/config.xml
<user_files_path>/var/lib/clickhouse/user_files/</user_files_path>
$ cat /var/lib/clickhouse/user_files/test.csv
1,2,3
3,2,1
78,43,45
Getting data from a table in test.csv
and selecting the first two rows from it:
SELECT * FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32') LIMIT 2;
┌─column1─┬─column2─┬─column3─┐
│ 1 │ 2 │ 3 │
│ 3 │ 2 │ 1 │
└─────────┴─────────┴─────────┘
Getting the first 10 lines of a table that contains 3 columns of UInt32 type from a CSV file:
SELECT * FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32') LIMIT 10;
Inserting data from a file into a table:
INSERT INTO FUNCTION file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32') VALUES (1, 2, 3), (3, 2, 1);
SELECT * FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32');
┌─column1─┬─column2─┬─column3─┐
│ 1 │ 2 │ 3 │
│ 3 │ 2 │ 1 │
└─────────┴─────────┴─────────┘
Globs in Path
Multiple path components can have globs. For being processed file must exist and match to the whole path pattern (not only suffix or prefix).
*
— Substitutes any number of any characters except/
including empty string.?
— Substitutes any single character.{some_string,another_string,yet_another_one}
— Substitutes any of strings'some_string', 'another_string', 'yet_another_one'
.{N..M}
— Substitutes any number in range from N to M including both borders.**
- Fetches all files inside the folder recursively.
Constructions with {}
are similar to the remote table function.
Example
Suppose we have several files with the following relative paths:
- 'some_dir/some_file_1'
- 'some_dir/some_file_2'
- 'some_dir/some_file_3'
- 'another_dir/some_file_1'
- 'another_dir/some_file_2'
- 'another_dir/some_file_3'
Query the number of rows in these files:
SELECT count(*) FROM file('{some,another}_dir/some_file_{1..3}', 'TSV', 'name String, value UInt32');
Query the number of rows in all files of these two directories:
SELECT count(*) FROM file('{some,another}_dir/*', 'TSV', 'name String, value UInt32');
:::warning
If your listing of files contains number ranges with leading zeros, use the construction with braces for each digit separately or use ?
.
:::
Example
Query the data from files named file000
, file001
, … , file999
:
SELECT count(*) FROM file('big_dir/file{0..9}{0..9}{0..9}', 'CSV', 'name String, value UInt32');
Example
Query the data from all files inside big_dir
directory recursively:
SELECT count(*) FROM file('big_dir/**', 'CSV', 'name String, value UInt32');
Example
Query the data from all file002
files from any folder inside big_dir
directory recursively:
SELECT count(*) FROM file('big_dir/**/file002', 'CSV', 'name String, value UInt32');
Virtual Columns
_path
— Path to the file._file
— Name of the file.
See Also