SQL交换一列中数据的值(如男女性别)

在刷LeetCode的时候遇到的SQL题目 

627. Swap Salary

Given a table salary, such as the one below, that has m=male and f=female values. Swap all f and m values (i.e., change all f values to m and vice versa) with a single update query and no intermediate temp table.

For example:

| id | name | sex | salary |
|----|------|-----|--------|
| 1  | A    | m   | 2500   |
| 2  | B    | f   | 1500   |
| 3  | C    | m   | 5500   |
| 4  | D    | f   | 500    |
After running your query, the above salary table should have the following rows:
| id | name | sex | salary |
|----|------|-----|--------|
| 1  | A    | f   | 2500   |
| 2  | B    | m   | 1500   |
| 3  | C    | f   | 5500   |
| 4  | D    | m   | 500    |

大概就是要求交换表中sex列的性别

一开始想着用update salary set sex = f when sex = m再用个AND,后来一想这样执行的结果应该是错的、

然后就偷看了solution,才知道还有when case语句,所以记录一下

update salary
set sex = 
    case sex
        when 'm' then 'f'
        else 'm'
    end;


大概意思就是when m,then就设置为f,,else都设置为m



posted @ 2017-10-06 10:07  link98  阅读(600)  评论(0编辑  收藏  举报