MySQL中不使用临时表更新列数据
为此，请使用CASE语句。即使不使用临时表也可以使用。让我们首先创建一个表-
mysql> create table DemoTable -> ( -> UserName varchar(100), -> UserStatus varchar(100) -> ); Query OK, 0 rows affected (0.74 sec)
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable values('John','Active');
Query OK, 1 row affected (0.29 sec)
mysql> insert into DemoTable values('Chris','Inactive');
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable values('Bob','Inactive');
Query OK, 1 row affected (0.32 sec)
mysql> insert into DemoTable values('Robert','Active');
Query OK, 1 row affected (0.15 sec)使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
输出结果
这将产生以下输出-
+----------+------------+ | UserName | UserStatus | +----------+------------+ | John | Active | | Chris | Inactive | | Bob | Inactive | | Robert | Active | +----------+------------+ 4 rows in set (0.00 sec)
以下是使用CASE更新列数据的查询-
mysql> update DemoTable -> set UserStatus=CASE UserStatus WHEN 'Inactive' THEN 'Active' ELSE 'Inactive' END; Query OK, 4 rows affected (0.28 sec) Rows matched: 4 Changed: 4 Warnings: 0
让我们再次检查表记录-
mysql> select *from DemoTable;
输出结果
这将产生以下输出-
+----------+------------+ | UserName | UserStatus | +----------+------------+ | John | Inactive | | Chris | Active | | Bob | Active | | Robert | Inactive | +----------+------------+ 4 rows in set (0.00 sec)