Learn about the CSV storage engine in MariaDB Server. Understand how to manage data stored as comma-separated values, making it ideal for data import, export, and exchange.
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 is the default storage engine when using logging of SQL queries to tables.
mysqld --log-output=tableWhen 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.
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.
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 columnsCreating, 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"This page is licensed: CC BY-SA / Gnu FDL
CSV tables support the CHECK TABLE and REPAIR TABLE statements.
CHECK TABLE will mark the table as corrupt if it finds a problem, while REPAIR TABLE will restore rows until the first corrupted row, discarding the rest.
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 | 2013-07-08 | one |
| 2 | 2013-07-08 | two |
| 3 | 2013-07-08 | three |
+---+------------+-------+Using an editor, the actual file will look as follows
$ cat csv_test.CSV
1,"2013-07-08","one"
2,"2013-07-08","two"
3,"2013-07-08","three"Let's introduce some corruption with an unwanted quote in the 2nd row:
1,"2013-07-08","one"
2","2013-07-08","two"
3,"2013-07-08","three"CHECK TABLE csv_test;
+---------------+-------+----------+----------+
| Table | Op | Msg_type | Msg_text |
+---------------+-------+----------+----------+
| test.csv_test | check | error | Corrupt |
+---------------+-------+----------+----------+We can repair this, but all rows from the corrupt row onwards will be lost:
REPAIR TABLE csv_test;
+---------------+--------+----------+----------------------------------------+
| Table | Op | Msg_type | Msg_text |
+---------------+--------+----------+----------------------------------------+
| test.csv_test | repair | Warning | Data truncated for column 'x' at row 2 |
| test.csv_test | repair | status | OK |
+---------------+--------+----------+----------------------------------------+
SELECT * FROM csv_test;
+---+------------+-----+
| x | y | z |
+---+------------+-----+
| 1 | 2013-07-08 | one |
+---+------------+-----+This page is licensed: CC BY-SA / Gnu FDL