# Time:  O(n)
# Space: O(1)

# 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    |

UPDATE salary SET sex = IF(sex = 'm', 'f', 'm')