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

解答：题目是交换薪水，实际是反转性别，通用方法需要一点点判断：

UPDATE salary set sex = CASE sex WHEN 'm' then 'f' else 'm' end;

或者写成Case搜索函数的形式：

UPDATE salary set sex = CASE WHEN sex = 'm' then 'f' else 'm' end;

MARK一下leetCode网友的两条超短语句：

UPDATE salary set sex = IF(sex='m','f','m');
UPDATE salary set sex =CHAR((ASCII('f')^ASCII('m')^ASCII(sex)));