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CHANGE COLUMN
TiDB 数据库中 CHANGE COLUMN 的使用概况。
/docs-cn/dev/sql-statements/sql-statement-change-column/
/docs-cn/dev/reference/sql/statements/change-column/

CHANGE COLUMN

ALTER TABLE.. CHANGE COLUMN 语句用于在已有表上更改列，包括对列进行重命名，和将数据改为兼容类型。

语法图

AlterTableStmt:

AlterTableStmt

AlterTableSpec:

AlterTableSpec

ColumnName:

ColumnName

ColumnDef:

ColumnDef

ColumnPosition:

ColumnPosition

示例

{{< copyable "sql" >}}

CREATE TABLE t1 (id int not null primary key AUTO_INCREMENT, col1 INT);
Query OK, 0 rows affected (0.11 sec)

{{< copyable "sql" >}}

INSERT INTO t1 (col1) VALUES (1),(2),(3),(4),(5);
Query OK, 5 rows affected (0.02 sec)
Records: 5  Duplicates: 0  Warnings: 0

{{< copyable "sql" >}}

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

{{< copyable "sql" >}}

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

{{< copyable "sql" >}}

ALTER TABLE t1 CHANGE col3 col3 INT;
ERROR 1105 (HY000): unsupported modify column length 11 is less than origin 20

{{< copyable "sql" >}}

ALTER TABLE t1 CHANGE col3 col3 BLOB;
ERROR 1105 (HY000): unsupported modify column type 252 not match origin 8

{{< copyable "sql" >}}

ALTER TABLE t1 CHANGE col3 col4 BIGINT, CHANGE id id2 INT NOT NULL;
ERROR 1105 (HY000): can't run multi schema change

MySQL 兼容性

  • 不支持在单个 ALTER TABLE 语句中进行多个更改。
  • 不支持有损变更，比如从 BIGINT 变为 INTEGER，或者从 VARCHAR(255) 变为 VARCHAR(10)。
  • 不支持修改 DECIMAL 类型的精度。
  • 不支持更改 UNSIGNED 属性。

另请参阅