file

Creates a table from a file.

  1. file(path, format, structure)

Input parameters

  • path — The relative path to the file from user_files_path. Path to file support following globs in readonly mode: *, ?, {abc,def} and {N..M} where N, 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.

Example

Setting user_files_path and the contents of the file test.csv:

  1. $ grep user_files_path /etc/clickhouse-server/config.xml
  2.     <user_files_path>/var/lib/clickhouse/user_files/</user_files_path>
  4. $ cat /var/lib/clickhouse/user_files/test.csv
  5.     1,2,3
  6.     3,2,1
  7.     78,43,45

Table fromtest.csv and selection of the first two rows from it:

  1. SELECT *
  2. FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32')
  3. LIMIT 2
  1. ┌─column1─┬─column2─┬─column3─┐
  2. │       1 │       2 │       3 │
  3. │       3 │       2 │       1 │
  4. └─────────┴─────────┴─────────┘
  1. -- getting the first 10 lines of a table that contains 3 columns of UInt32 type from a CSV file
  2. SELECT * FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32') LIMIT 10

Globs in path

  • * — Matches any number of any characters including none.
  • ? — Matches any single character.
  • {some_string,another_string,yet_another_one} — Matches any of strings 'some_string', 'another_string', 'yet_another_one'.
  • {N..M} — Matches any number in range from N to M including both borders.

Warning

If your listing of files contains number ranges with leading zeros, use the construction with braces for each digit separately or use ?.

Multiple path components can have globs. For being processed file should exists and matches to the whole path pattern.

Original article