sql leetcode 627. Swap Salary

leetcode现在居然加入了sql题，真是涵盖万千啊。

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    |

解法有2种。

第一种：使用条件语句：

UPDATE salary    SET sex  = (CASE WHEN sex = 'm'                 THEN  'f'                 ELSE 'm'                 END)

或者

UPDATE salary SET sex = IF(sex = 'm', 'f', 'm')

第二种：使用异或：

update salary set sex = CHAR(ASCII('f') ^ ASCII('m') ^ ASCII(sex));