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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:

AlterTableStmt

AlterTableSpec:

AlterTableSpec

ColumnKeywordOpt:

ColumnKeywordOpt

ColumnName:

ColumnName

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> 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

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