CHANGE COLUMN

The ALTER TABLE.. CHANGE COLUMN statement changes a column on an existing table. The change can include both renaming the column, and changing the data type to a compatible type.

Synopsis

AlterTableStmt:

AlterTableSpec:

ColumnKeywordOpt:

ColumnName:

ColumnDef:

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>
mysql> ALTER TABLE t1 CHANGE col1 col2 INT;
Query OK, 0 rows affected (0.09 sec)

mysql> ALTER TABLE t1 CHANGE col2 col3 BIGINT, ALGORITHM=INSTANT;
Query OK, 0 rows affected (0.08 sec)

mysql>
mysql> ALTER TABLE t1 CHANGE col3 col3 INT;
ERROR 1105 (HY000): unsupported modify column length 11 is less than origin 20
mysql> ALTER TABLE t1 CHANGE col3 col3 BLOB;
ERROR 1105 (HY000): unsupported modify column type 252 not match origin 8
mysql> ALTER TABLE t1 CHANGE col3 col4 BIGINT, CHANGE id id2 INT 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.

See also

• CREATE TABLE
• SHOW CREATE TABLE
• ADD COLUMN
• DROP COLUMN
• MODIFY COLUMN