Neat and Easy Solution
#Solution\n\nUPDATE Salary\nSET sex = \nCASE\n    WHEN sex = "f" THEN "m"\n    WHEN sex = "m" THEN "f"\nEND
**#Solution**\n\nUPDATE Salary\nSET sex = \nCASE\n    WHEN sex = "f" THEN "m"\n    WHEN sex = "m" THEN "f"\nEND
['Ordered Set', 'MySQL']