ADD COLUMN
ALTER TABLE.. ADD COLUMN
语句用于在已有表中添加列。在 TiDB 中,ADD COLUMN
为在线操作,不会阻塞表中的数据读写。
语法图
AlterTableStmt:
AlterTableSpec:
ColumnKeywordOpt:
ColumnDef:
ColumnPosition:
示例
CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT);
Query OK, 0 rows affected (0.11 sec)
INSERT INTO t1 VALUES (NULL);
Query OK, 1 row affected (0.02 sec)
SELECT * FROM t1;
+----+
| id |
+----+
| 1 |
+----+
1 row in set (0.00 sec)
ALTER TABLE t1 ADD COLUMN c1 INT NOT NULL;
Query OK, 0 rows affected (0.28 sec)
SELECT * FROM t1;
+----+----+
| id | c1 |
+----+----+
| 1 | 0 |
+----+----+
1 row in set (0.00 sec)
ALTER TABLE t1 ADD c2 INT NOT NULL AFTER c1;
Query OK, 0 rows affected (0.28 sec)
SELECT * FROM t1;
+----+----+----+
| id | c1 | c2 |
+----+----+----+
| 1 | 0 | 0 |
+----+----+----+
1 row in set (0.00 sec)
MySQL 兼容性
- 不支持同时添加多列。
- 不支持将新添加的列设为
PRIMARY KEY
。 - 不支持将新添加的列设为
AUTO_INCREMENT
。