627. Swap Salary--UPDATE and CASE...WHEN

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    |

Approach: Using UPDATE and CASE...WHEN [Accepted]

Algorithm

To dynamically set a value to a column, we can use UPDATE statement together when CASE...WHEN... flow control statement.

MySQL

UPDATE salarySET    sex = CASE sex        WHEN 'm' THEN 'f'        ELSE 'm'    END;