When a CREATE TABLE or ALTER TABLE command is issued, MariaDB will silently change a column specification in the following cases:

  • PRIMARY KEY columns are always NOT NULL.
  • Any trailing spaces from SET and ENUM values are discarded.
  • TIMESTAMP columns are always NOT NULL, and display sizes are discarded
  • A row-size limit of 65535 bytes applies
  • If strict SQL mode is not enabled, a VARCHAR column longer than 65535 become TEXT, and a VARBINARY columns longer than 65535 becomes a BLOB. If strict mode is enabled the silent changes will not be made, and an error will occur.
  • If a USING clause specifies an index that's not permitted by the storage engine, the engine will instead use another available index type that can be applied without affecting results.
  • If the CHARACTER SET binary attribute is specified, the column is created as the matching binary data type. A TEXT becomes a BLOB, CHAR a BINARY and VARCHAR a VARBINARY. ENUMs and SETs are created as defined.

To ease imports from other RDBMS's, MariaDB will also silently map the following data types:

Other Vendor TypeMariaDB Type
BOOLTINYINT
BOOLEANTINYINT
CHARACTER VARYING(M)VARCHAR(M)
FIXEDDECIMAL
FLOAT4FLOAT
FLOAT8DOUBLE
INT1TINYINT
INT2SMALLINT
INT3MEDIUMINT
INT4INT
INT8BIGINT
LONG VARBINARYMEDIUMBLOB
LONG VARCHARMEDIUMTEXT
LONGMEDIUMTEXT
MIDDLEINTMEDIUMINT
NUMERICDECIMAL

Currently, all MySQL types are supported in MariaDB.

For type mapping between Cassandra and MariaDB, see Cassandra storage engine.

Example

Silent changes in action:

CREATE TABLE SilenceIsGolden
   (
    f1 TEXT CHARACTER SET binary,
    f2 VARCHAR(15) CHARACTER SET binary,
    f3 CHAR CHARACTER SET binary,
    f4 ENUM('x','y','z') CHARACTER SET binary,
    f5 VARCHAR (65536),
    f6 VARBINARY (65536),
    f7 INT1
   );
Query OK, 0 rows affected, 2 warnings (0.31 sec)

SHOW WARNINGS;
+-------+------+-----------------------------------------------+
| Level | Code | Message                                       |
+-------+------+-----------------------------------------------+
| Note  | 1246 | Converting column 'f5' from VARCHAR to TEXT   |
| Note  | 1246 | Converting column 'f6' from VARBINARY to BLOB |
+-------+------+-----------------------------------------------+

DESCRIBE SilenceIsGolden;
+-------+-------------------+------+-----+---------+-------+
| Field | Type              | Null | Key | Default | Extra |
+-------+-------------------+------+-----+---------+-------+
| f1    | blob              | YES  |     | NULL    |       |
| f2    | varbinary(15)     | YES  |     | NULL    |       |
| f3    | binary(1)         | YES  |     | NULL    |       |
| f4    | enum('x','y','z') | YES  |     | NULL    |       |
| f5    | mediumtext        | YES  |     | NULL    |       |
| f6    | mediumblob        | YES  |     | NULL    |       |
| f7    | tinyint(4)        | YES  |     | NULL    |       |
+-------+-------------------+------+-----+---------+-------+

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