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Document Feedback

Change the length of an unconstrained column

Last Updated：2026-04-14 07:41:43 Updated

This topic describes incompatibilities between MySQL databases and MySQL tenants of OceanBase Database when you change the length of an unconstrained column.

The following table describes the operations that you can perform to change the length of a column by executing the ALTER TABLE table_name MODIFY/CHANGE COLUMN DDL statement in a MySQL database and a MySQL tenant of OceanBase Database.

Note

In the table, a hyphen (-) indicates none.

Column type in a MySQL database	Allowed operation	Column type in a MySQL tenant of OceanBase Database	Allowed operation
INT	Increase and decrease the length	INTEGER	Increase and decrease the length
TINYINT	Increase and decrease the length	TINYINT	Increase and decrease the length
SMALLINT	Increase and decrease the length	SMALLINT	Increase and decrease the length
MEDIUMINT	Increase and decrease the length	MEDIUMINT	Increase and decrease the length
BIGINT	Increase and decrease the length	BIGINT	Increase and decrease the length
BOOL	-	BOOLEAN	-
DECIMAL	Increase and decrease the length	DECIMAL	Increase the length
NUMERIC	Increase and decrease the length	NUMERIC	Increase the length
REAL	Increase and decrease the length	FLOAT	Increase and decrease the length
DOUBLE	Increase and decrease the length	DOUBLE	Increase and decrease the length
FLOAT	Increase and decrease the length	FLOAT	Increase and decrease the length
BIT	Increase and decrease the length	BIT	Increase and decrease the length
CHAR	Increase and decrease the length	CHAR	Increase the length
NCHAR	Increase and decrease the length	CHAR	Increase the length
VARCHAR	Increase and decrease the length	VARCHAR	Increase the length
BINARY	Increase and decrease the length	BINARY	-
VARBINARY	Increase and decrease the length	VARBINARY	Increase the length
LONG_VARBINARY	-	BLOB	-
YEAR	Increase and decrease the length	YEAR	Increase the length (the length is fixed to be 4 bytes)
DATE	-	DATE	-
TIME	Increase and decrease the length	TIME	Increase the length
TIMESTAMP	Increase and decrease the length	TIMESTAMP	Increase the length
DATETIME	Increase and decrease the length	DATETIME	Increase the length
TINYBLOB	-	TINYBLOB	-
MEDIUMBLOB	-	MEDIUMBLOB	-
BLOB	-	BLOB	-
LONGBLOB	-	LONGBLOB	-
TINYTEXT	-	TINYTEXT	-
MEDIUMTEXT	-	MEDIUMTEXT	-
TEXT	-	TEXT	-
LONGTEXT	-	LONGTEXT	-
ENUM	Increase and decrease the length	ENUM	Increase the length
SET	Increase and decrease the length	SET	Increase the length
JSON	-	JSON	-

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