Swap Salary

题目

Given a tablesalary, 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    |

SQL Schema:

create table if not exists salary(id int, name varchar(100), sex char(1), salary int);
Truncate table salary;
insert into salary (id, name, sex, salary) values ('1', 'A', 'm', '2500');
insert into salary (id, name, sex, salary) values ('2', 'B', 'f', '1500');
insert into salary (id, name, sex, salary) values ('3', 'C', 'm', '5500');
insert into salary (id, name, sex, salary) values ('4', 'D', 'f', '500');

思路分析

这道题就是用case if else condition来实现

# Write your MySQL query statement below
update salary
set sex = (case when sex = 'm' then 'f' else 'm' end)；