About CSV

Lo Storage Engine può leggere e scrivere nei file registrati nel formato CSV (comma-separated-values).

Lo Storage Engine CSV e il logging sulle tabelle

Lo Storage Engine CSV è quello utilizzato per default per il logging delle query SQL nelle tabelle.

mysqld --log-output=table

Lo Storage Engine CSV e NOT NULL

Lo Storage Engine CSV non supporta le colonne con valori NULL e se si cerca di creare una tabella CSV con tali colonne si ottiene un errore:

MariaDB [test]> 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

Si può invece aggiungere NOT NULL alle definizioni di ogni colonna.

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.

Examples

MariaDB [test]> CREATE TABLE csv_test (
    -> x INT NOT NULL, y DATE NOT NULL, z CHAR(10) NOT NULL
    -> ) ENGINE=CSV;
Query OK, 0 rows affected (0.11 sec)

MariaDB [test]> INSERT INTO csv_test VALUES
    -> (1,CURDATE(),'one'),
    -> (2,CURDATE(),'two'),
    -> (3,CURDATE(),'three');
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

MariaDB [test]> SELECT * FROM csv_test;
+---+------------+-------+
| x | y          | z     |
+---+------------+-------+
| 1 | 2011-11-16 | one   |
| 2 | 2011-11-16 | two   |
| 3 | 2011-11-16 | three |
+---+------------+-------+
3 rows in set (0.00 sec)

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

See Also

• http://dev.mysql.com/doc/refman/5.1/en/csv-storage-engine.html