leetcode题目：
要求：
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 statement and no intermediate temp table.
Note that you must write a single update statement, DO NOT write any select statement for this problem.
Example:
| id | name | sex | salary | |----|------|-----|--------| | 1 | A | m | 2500 | | 2 | B | f | 1500 | | 3 | C | m | 5500 | | 4 | D | f | 500 |
After running your update statement, 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 |
答案：使用case then 按条件给字段赋值
# Write your MySQL query statement below
UPDATE salary
SET sex = case when sex = 'f' then 'm'
when sex = 'm' then 'f'
end