DROP COLUMN

DROP COLUMN 语句用于从指定的表中删除列。在 TiDB 中，COLUMN 为在线操作，不会阻塞表中的数据读写。

语法图

AlterTableStmt:

AlterTableSpec:

ColumnKeywordOpt:

ColumnName:

示例

mysql> CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY auto_increment, col1 INT NOT NULL, col2 INT NOT NULL);
Query OK, 0 rows affected (0.12 sec)
mysql> INSERT INTO t1 (col1,col2) VALUES (1,1),(2,2),(3,3),(4,4),(5,5);
Query OK, 5 rows affected (0.02 sec)
Records: 5  Duplicates: 0  Warnings: 0
mysql> SELECT * FROM t1;
+----+------+------+
| id | col1 | col2 |
+----+------+------+
|  1 |    1 |    1 |
|  2 |    2 |    2 |
|  3 |    3 |    3 |
|  4 |    4 |    4 |
|  5 |    5 |    5 |
+----+------+------+
5 rows in set (0.01 sec)
mysql> ALTER TABLE t1 DROP COLUMN col1, DROP COLUMN col2;
ERROR 1105 (HY000): can't run multi schema change
mysql> SELECT * FROM t1;
+----+------+------+
| id | col1 | col2 |
+----+------+------+
|  1 |    1 |    1 |
|  2 |    2 |    2 |
|  3 |    3 |    3 |
|  4 |    4 |    4 |
|  5 |    5 |    5 |
+----+------+------+
5 rows in set (0.00 sec)
mysql> ALTER TABLE t1 DROP COLUMN col1;
Query OK, 0 rows affected (0.27 sec)
mysql> SELECT * FROM t1;
+----+------+
| id | col2 |
+----+------+
|  1 |    1 |
|  2 |    2 |
|  3 |    3 |
|  4 |    4 |
|  5 |    5 |
+----+------+
5 rows in set (0.00 sec)

MySQL 兼容性

• 不支持使用相同语句删除多个列。

另请参阅

• ADD COLUMN
• SHOW CREATE TABLE
• CREATE TABLE