1.題目
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.
翻譯:給定一張表salary,就像下面那張一樣,有m代表male和f代表female.交換所有的 f 和 m 值(例如,把所有的 f 值更改爲m,反之亦然)。用一個更新查詢語句,不要用臨時表。
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 |
2.思路
更新sex列的值,需要用到if-else語句;
3.算法
update salary
set sex=if(sex='m','f','m')
4.總結
sql中的if語句; if(判別式,判別式成立的結果,不成立的結果)