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

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