text: '''
  from leetcode!
  
  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 temp table(s).
  
  Note that you must write a single update 
  statement, DO NOT write any select statement for this problem.
  '''
  
  
  update salary
  set sex = case when sex = 'f' then 'm'
                 when sex = 'm' then 'f'
                 end 
                 
  