Explore Silent Column Changes in MariaDB. Learn when the server automatically modifies column definitions or data types during table creation to ensure engine compatibility.
When a CREATE TABLE or ALTER TABLE command is issued, MariaDB silently changes a column specification in the following cases:
PRIMARY KEY columns are always NOT NULL.
TIMESTAMP columns are always NOT NULL, and display sizes are discarded.
A row-size limit of 65535 bytes applies.
If is not enabled (by default, it is), a column longer than 65535 become , and a columns longer than 65535 becomes a . 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 RDBMSs, MariaDB also silently maps the following data types:
Currently, all MySQL types are supported in MariaDB.
For type mapping between Cassandra and MariaDB, see .
Silent changes in action:
This page is licensed: CC BY-SA / Gnu FDL
INT1
INT2
INT3
INT4
INT8
LONG VARBINARY
LONG VARCHAR
LONG
MIDDLEINT
NUMERIC
BOOL
BOOLEAN
CHARACTER VARYING(M)
VARCHAR(M)
FIXED
FLOAT4
FLOAT8
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 | |
+-------+-------------------+------+-----+---------+-------+