【leetcode】627. Swap Salary

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一、题目描述

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    |

思路：这道题有个思路厉害了，采用异或的方式，将sex = sex ^ 'f' ^ 'm'，因为f ^ f = 0，m^m=0，所以第一份代码如下：

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

这种思路可以应用到所有进行交换的题的中！！

常规思路代码：

update salary set sex = (CASE WHEN sex = 'f'                        THEN 'm'                        ELSE 'f'                        END)

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