Question

I’m trying to get a list of IDs from three tables.

table_one
---------
| id | other_data |

table_two
---------
| this_id | user_id | time_qual |

table_three
---------
| this_id | second_qual |

I want to get a list back of table_one ids with the following qualifications:

1. the id is also found in table_three‘s this_id
2. second_qual in table_three is equal to 1
3. this_id in table_two equals table_one‘s id AND in the same row, table_two‘s user_id equals the php variable $user_id AND time_qual in that row equals 1.
4. but also include ids that qualify for #1 and #2, and not #3 if table_one‘s id and the php variable $user_id isn’t found on the same row of table_two

This is my attempt:

        SELECT tb1.id FROM table_one tb1
          INNER JOIN table_two tb2
          INNER JOIN table_three tb3
          WHERE tb2.this_id = tb1.id
           AND tb3.this_id = tb1.id
           AND tb3.second_qual = 1
           AND ((tb2.user_id = $user_id AND tb2.time_qual = 1)
              OR ($user_id NOT IN (SELECT user_id FROM table_two)))
           GROUP BY tb1.id

I’m guessing there should be a UNION in there and that tb2.this_id = tb1.id eliminates the results I want from #4, but I’m not sure what to do.

Thanks in advance!

Answer 1

To the best of my ability to parse your requirements, I think this is the answer. Let me know if it misses and I can amend:

SELECT t1.id
FROM table_three t3 
RIGHT JOIN table_one t1 
  ON t1.id=t3.this_id 
LEFT JOIN table_two t2 
  ON t1.id=t2.this_id 
WHERE (t3.this_id IS NOT NULL AND t3.second_qual=1) 
  AND ((t2.this_id IS NOT NULL AND t2.user_id=1 AND t2.time_qual=1) 
    OR t2.this_id IS NULL);