跨行交换列值

Question

我想更新 emp 的姓氏和名字。表示第一个 emp 名称应更新为第五个 emp。

id,firstname
1,john
2,pall
3,kevin
4,Alan

结果应该是

id,firstname
1,kevin
2,Alan
3,john
4,pall

Answer 1

根据您提供给我们的有限信息，解决方案如下所示：

update emp
   set firstname = case id
                    when 1 then (select firstname from emp where id = 3)
                    when 2 then (select firstname from emp where id = 4) 
                    when 3 then (select firstname from emp where id = 1)
                    when 4 then (select firstname from emp where id = 2)
                 end
where id in (1,2,3,4);