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MODIFY COLUMN

The ALTER TABLE.. MODIFY COLUMN statement modifies a column on an existing table. The modification can include changing the data type and attributes. To rename at the same time, use the CHANGE COLUMN statement instead.

Synopsis

AlterTableStmt:

AlterTableStmt

AlterTableSpec:

AlterTableSpec

ColumnKeywordOpt:

ColumnKeywordOpt

ColumnDef:

ColumnDef

ColumnPosition:

ColumnPosition

Examples

mysql> CREATE TABLE t1 (id int not null primary key AUTO_INCREMENT, col1 INT); Query OK, 0 rows affected (0.11 sec) mysql> INSERT INTO t1 (col1) VALUES (1),(2),(3),(4),(5); Query OK, 5 rows affected (0.02 sec) Records: 5 Duplicates: 0 Warnings: 0 mysql> ALTER TABLE t1 MODIFY col1 BIGINT; Query OK, 0 rows affected (0.09 sec) mysql> SHOW CREATE TABLE t1\G *************************** 1. row *************************** Table: t1 Create Table: CREATE TABLE `t1` ( `id` int(11) NOT NULL AUTO_INCREMENT, `col1` bigint(20) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin AUTO_INCREMENT=30001 1 row in set (0.00 sec) mysql> ALTER TABLE t1 MODIFY col1 INT; ERROR 1105 (HY000): unsupported modify column length 11 is less than origin 20 mysql> ALTER TABLE t1 MODIFY col1 BLOB; ERROR 1105 (HY000): unsupported modify column type 252 not match origin 8 mysql> ALTER TABLE t1 MODIFY col1 BIGINT, MODIFY id BIGINT NOT NULL; ERROR 1105 (HY000): can't run multi schema change

MySQL compatibility

  • Making multiple changes in a single ALTER TABLE statement is not currently supported.
  • Only certain types of data type changes are supported. For example, an INTEGER to BIGINT is supported, but the reverse is not possible. Changing from an integer to a string format or blob is not supported.
  • Modifying precision of the DECIMAL data type is not supported.

See also

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