MySQL 命令行刪除表字段：ALTER TABLE DROP COLUMN 實戰驗證

語法

ALTER TABLE tbl DROP COLUMN col_name;

實戰演示

刪除前結構

mysql> SELECT * FROM test;
+------+--------+-------+------------+------------+------------+------------+
| t_id | t_name | t_password | t_birth | birth      | birth1     | birth2     |
+------+--------+-------+------------+------------+------------+------------+
| 1    | name1  | ...   | NULL       | 1990-01-01 | 0000-00-00 | 2013-01-01 |
| 2    | name2  | ...   | 2013-01-01 | NULL       | 0000-00-00 | 2013-01-01 |
+------+--------+-------+------------+------------+------------+------------+

執行刪除

mysql> ALTER TABLE test DROP COLUMN birth1;
Query OK, 0 rows affected (0.13 sec)

刪除後驗證

mysql> SELECT * FROM test;
+------+--------+-------+------------+------------+------------+
| t_id | t_name | t_password | t_birth | birth      | birth2     |
+------+--------+-------+------------+------------+------------+
| 1    | name1  | ...   | NULL       | 1990-01-01 | 2013-01-01 |
| 2    | name2  | ...   | 2013-01-01 | NULL       | 2013-01-01 |
+------+--------+-------+------------+------------+------------+

birth1 字段已移除，其餘數據完好。

注意事項

• 刪除字段會**永久丟失數據**，操作前請備份
• 若字段有索引、外鍵、被視圖/存儲過程引用，需先刪除依賴對象
• 大表刪除字段會重建表，鎖表時間長，建議低峰期或用 pt-online-schema-change 在線變更