Question

I have table test contain 4 fields

+----+-----------+--------------+-----+
| id | int_value | string_value | qid |
+----+-----------+--------------+-----+
|  1 |       111 | Red          |   1 |
|  2 |       111 | Green        |   2 |
|  3 |       111 | Blue         |   3 |
|  4 |       222 | Yellow       |   1 |
|  5 |       222 | Red          |   2 |
|  6 |       333 | Red          |   1 |
|  7 |       333 | Green        |   2 |
+----+-----------+--------------+-----+

I want to query int_value that match flowing constraints.

(qid = 1 and string_value = 'Red') and (qid = 2 and string_value = "Green")

The result could be 111 and 333

It’s not make sense if I apply this statement

select int_value from test 
where (qid = 1 and string_value = 'Red') 
and (qid = 2 and string_value = "Green")

Does one can help me?
Thank you.

Answer 1

You could use a trick with COUNT:

SELECT int_value
FROM test
WHERE (
    (qid = 1 AND string_value = 'Red')  
    OR (qid = 2 AND string_value = 'Green')
)
GROUP BY int_value
HAVING COUNT(DISTINCT qid, string_value) = 2

This is completely untested, though, so I’m not sure if even the syntax is correct. Basically it groups the results by the int_value, and finds any group where there’s as many results as there are different cases. You need to have the numeric value in the HAVING clause match the number of OR alternatives.