Leetcode 647
Problem
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.
Examples
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’.
Solution
Method 1 - Using if
Code
Sql
UPDATE salary SET sex = IF(sex='f','m','f');
Method 2 - Using Case Expression
Code
Sql
UPDATE salary
SET sex = (CASE WHEN sex = 'm'
THEN 'f'
ELSE 'm'
END)
Method 3 - Xor and Ascii
Code
Sql
update salary set sex = CHAR(ASCII('f') ^ ASCII('m') ^ ASCII(sex));
Method 4 - Ascii and Sum
Code
Sql
update salary set sex= CHAR(ASCII('f') + ASCII('m') - ASCII(sex));