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

It's possible. The particular syntax depends on how you store 'good' and 'bad' reviews.

Suppose you had a classification column in review that had values 'good' and 'bad'.

Then you could do:

SELECT employee.*
FROM employee
JOIN review 
 ON employee.id=review.employee_id
GROUP BY employee.id
HAVING SUM(IF(classification='good',1,0))>0 -- count up #good reviews, > 0
   AND SUM(IF(classification='bad',1,0))=0  -- count up #bad  reviews, = 0.