如何通过交换两个列值来更新MySQL表？
要交换列中的两个值，请使用CASEWHEN语句。让我们首先创建一个表-
mysql> create table DemoTable1382 -> ( -> StudentName varchar(20) -> );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable1382 values('John');
mysql> insert into DemoTable1382 values('Chris');
mysql> insert into DemoTable1382 values('Adam');
mysql> insert into DemoTable1382 values('Bob');使用select语句显示表中的所有记录-
mysql> select * from DemoTable1382;
这将产生以下输出-
+-------------+ | StudentName | +-------------+ | John | | Chris | | Adam | | Bob | +-------------+ 4 rows in set (0.00 sec)
以下是通过交换两个列值来更新MySQL表的查询-
mysql> update DemoTable1382 -> set StudentName=( case when StudentName="Chris" then "John" -> when StudentName="John" then "Chris" -> else -> StudentName -> end -> ); Rows matched: 4 Changed: 2 Warnings: 0
让我们再次检查表记录-
mysql> select * from DemoTable1382;
这将产生以下输出-
+-------------+ | StudentName | +-------------+ | Chris | | John | | Adam | | Bob | +-------------+ 4 rows in set (0.00 sec)