[SQL]LeetCode627. 交換工資 | Swap Salary

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SQL架構

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

---

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    |

---

給定一個 salary表，以下所示，有m=男性 和 f=女性的值 。交換全部的 f 和 m 值(例如，將全部 f 值更改成 m，反之亦然)。要求使用一個更新查詢，而且沒有中間臨時表。

例如:

| id | name | sex | salary |
|----|------|-----|--------|
| 1  | A    | m   | 2500   |
| 2  | B    | f   | 1500   |
| 3  | C    | m   | 5500   |
| 4  | D    | f   | 500    |

運行你所編寫的查詢語句以後，將會獲得如下表:

| id | name | sex | salary |
|----|------|-----|--------|
| 1  | A    | f   | 2500   |
| 2  | B    | m   | 1500   |
| 3  | C    | f   | 5500   |
| 4  | D    | m   | 500    |

---

129ms

1 # Write your MySQL query statement below
2 select id, name, if(sex = 'm','f','m') sex,salary from salary; 

---

281ms

1 UPDATE salary
2 SET sex = CASE
3 WHEN sex = 'f' THEN 'm'
4 ELSE 'f'
5 END

---

282ms

1 # Write your MySQL query statement below
2 update salary set sex= if(sex='m','f','m');

---

283ms

1 # Write your MySQL query statement below
2 UPDATE salary
3 SET
4     sex = CASE sex
5         WHEN 'm' THEN 'f'
6         ELSE 'm'
7     END;

---

284ms

1 update salary set sex=case sex when 'm' then 'f' else 'm' end;

---

287ms

1 # Write your MySQL query statement below
2 update salary set sex= CHAR(ASCII('f') + ASCII('m') - ASCII(sex));