[LeetCode] 627. Swap Salary

627. Swap Salary

Easy

SQL Schema

Table: Salary

+-------------+----------+
| Column Name | Type     |
+-------------+----------+
| id          | int      |
| name        | varchar  |
| sex         | ENUM     |
| salary      | int      |
+-------------+----------+
id is the primary key for this table.
The sex column is ENUM value of type ('m', 'f').
The table contains information about an employee.

 

Write an SQL query to 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 temporary tables.

Note that you must write a single update statement, do not write any select statement for this problem.

The query result format is in the following example.

 

Example 1:

Input: 
Salary table:
+----+------+-----+--------+
| id | name | sex | salary |
+----+------+-----+--------+
| 1  | A    | m   | 2500   |
| 2  | B    | f   | 1500   |
| 3  | C    | m   | 5500   |
| 4  | D    | f   | 500    |
+----+------+-----+--------+
Output: 
+----+------+-----+--------+
| id | name | sex | salary |
+----+------+-----+--------+
| 1  | A    | f   | 2500   |
| 2  | B    | m   | 1500   |
| 3  | C    | f   | 5500   |
| 4  | D    | m   | 500    |
+----+------+-----+--------+
Explanation: 
(1, A) and (3, C) were changed from 'm' to 'f'.
(2, B) and (4, D) were changed from 'f' to 'm'.

---

문제 풀이

• 주어진 salary 테이블에서 sex(성별)을 치환해야한다.
• m은 f로 f는 m으로 치환해야한다.
• salary 테이블을 update를 사용해서 값을 변경할 수 있는데, when과 case를 사용할 수 있고 if문을 사용해서 풀 수 있다. 

소스 코드

When

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

If

# if
update salary set sex = if(sex = 'm', 'f', 'm')