ClickHouse/docs/en/query_language/table_functions/file.md

file

Creates a table from a file.

file(path, format, structure)

Input parameters

• path — The relative path to the file from user_files_path.
• format — The format of the file.
• structure — Structure of the table. Format 'colunmn1_name column1_ype, 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:

$ 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

Table fromtest.csv and selection of 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

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