text: /*
  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 statement and no intermediate temp table.
  
  Note that you must write a single update statement, DO NOT write any select statement for this problem.
  
  Example:
  
  | id | name | sex | salary |
  |----|------|-----|--------|
  | 1  | A    | m   | 2500   |
  | 2  | B    | f   | 1500   |
  | 3  | C    | m   | 5500   |
  | 4  | D    | f   | 500    |
  
  After running your update statement, 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    |
  */
  
  -- Solution 
  update salary
  set
      sex = case when sex = 'm' then 'f'
                 when sex = 'f' then 'm'
                 else sex
  end;