数据删除

MySQL 删除字段中的值

MySQL 表中使用 DELETE 语句来删除数据

使用 DELETE 语句来删除数据，语法如下：

DELETE FROM 表名 WHERE 列=值;

示例：

DELETE FROM Username WHERE id=1;

删除成功如下：

mysql> DELETE FROM Username WHERE id=1;
Query OK, 1 row affected (0.01 sec)

mysql> select * from Username;
Empty set (0.00 sec)

MySQL 删除表中的字段

使用 ALTER TABLE ... DROP COLUMN ... 语句来删除字段，语法如下：

ALTER TABLE 表名 DROP COLUMN 字段名;

示例：

ALTER TABLE Username DROP COLUMN id;

删除成功如下：

mysql> ALTER TABLE Username DROP COLUMN id;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

// 原先表数据
mysql> select * from Username;
+------+------------+----------+
| id   | Username   | Password |
+------+------------+----------+
|    1 | steins_xin | 123456   |
+------+------------+----------+
1 row in set (0.00 sec)

//修改后表数据
mysql> select * from Username;
+------------+----------+
| Username   | Password |
+------------+----------+
| steins_xin | 123456   |
+------------+----------+
1 row in set (0.00 sec)

MySQL清空表数据

使用 DELETE FROM 语句来删除字段，语法如下：

DELETE FROM 表名;

示例：

DELETE FROM Username;

删除成功如下：

mysql> DELETE FROM Username;
Query OK, 1 row affected (0.00 sec)

mysql> select * from Username;
Empty set (0.00 sec)