CSV Overview

The CSV Storage Engine can read and append to files stored in CSV (comma-separated-values) format.

However, since MariaDB 10.0, a better storage engine is able to read and write such files: CONNECT.

The CSV storage engine and logging to tables

The CSV storage engine is the default storage engine when using logging of SQL queries to tables.

mysqld --log-output=table

CSV Storage Engine files

When you create a table using the CSV storage engine, three files are created:

• <table_name>.frm

• <table_name>.CSV

• <table_name>.CSM

The .frm file is the table format file.

The .CSV file is a plain text file. Data you enter into the table is stored as plain text in comma-separated-values format.

The .CSM file stores metadata about the table such as the state and the number of rows in the table.

Limitations

• CSV tables do not support indexing.

• CSV tables cannot be partitioned.

• Columns in CSV tables must be declared as NOT NULL.

• No transactions.

• The original CSV-format does not enable IETF-compatible parsing of embedded quote and comma characters. From MariaDB 10.1.8, it is possible to do so by setting the IETF_QUOTES option when creating a table.

Examples

Forgetting to add NOT NULL:

CREATE TABLE csv_test (x INT, y DATE, z CHAR(10)) ENGINE=CSV; ERROR 1178 (42000): The storage engine for the table doesn't support nullable columns

Creating, inserting and selecting:

CREATE TABLE csv_test (  x INT NOT NULL, y DATE NOT NULL, z CHAR(10) NOT NULL  ) ENGINE=CSV;

INSERT INTO csv_test VALUES  (1,CURDATE(),'one'),  (2,CURDATE(),'two'),  (3,CURDATE(),'three');

SELECT * FROM csv_test; +---+------------+-------+ | x | y | z | +---+------------+-------+ | 1 | 2011-11-16 | one | | 2 | 2011-11-16 | two | | 3 | 2011-11-16 | three | +---+------------+-------+

Viewing in a text editor:

$ cat csv_test.CSV 1,"2011-11-16","one" 2,"2011-11-16","two" 3,"2011-11-16","three"

See Also

• Checking and Repairing CSV Tables

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