At least one X but no Ys Query

Question

I come across this pattern occasionally and I haven\'t found a terribly satisfactory way to solve it.

Say I have a employee table and an review

Answer 1

The question -- return rows on side A based on nonexistence of a match in B -- (employees with No "Bad" reviews) describes an "anti-semi join". There are numerous ways to accomplish this kind of query, at least 5 I've discovered in MS Sql 2005 and above.

I know this solution works in MSSQL 2000 and above, and is the most efficient out of the 5 ways I've tried in MS Sql 2005 and 2008. I am not sure if it will work in MySQL, but it should, as it reflects a rather common set operation.

Note, the IN clause gives the subquery access to the employee table in the outer scope.

SELECT EE.*
FROM   employee EE
WHERE
    EE.EmpKey IN (
      SELECT RR.EmpKey
      FROM   review RR
      WHERE  RR.EmpKey = EE.EmpKey
        AND  RR.ScoreCategory = 'good'
    ) 
  AND
    EE.EmpKey NOT IN (
      SELECT  RR.EmpKey 
      FROM    review RR
      WHERE   RR.EmpKey = EE.EmpKey
        AND   RR.ScoreCategory = 'bad'
    )