Question

I have a MySQL table like this:

+----+------------+----------+
| id | instanceID | answerID |
+----+------------+----------+
| 1  | 1          | 10       |
| 2  | 1          | 12       |
| 3  | 1          | 20       |
| 4  | 2          | 12       |
| 5  | 2          | 20       |
| 6  | 2          | 22       |
| 7  | 2          | 25       |
| 8  | 3          | 20       |
| 9  | 3          | 25       |
| 10 | 4          | 12       |
| 11 | 4          | 20       |
+----+------------+----------+

I would like to retrieve the instanceID under certain conditions.

This is easy using ‘OR’:

SELECT instanceID FROM table WHERE (answerID = 10 OR answerID = 12) GROUP BY instanceID;
Returns:
1,2,4

However, ‘AND’ is not so simple, as the condition is applied to each individual row, rather than each instanceID.

For example, I would like to retrieve the instanceID where (answerID = 20 AND answerID = 25)
which should return 2,3

I need to avoid subqueries like WHERE x IN (subquery), as the table is biIIIIig.

This is a difficult concept to search for in search engines, so I resort to asking it here.

Thanks!

Answer 1

How about something like this:

select instanceid
from yourtable
where answerid in (20, 25)
group by instanceid
having count(distinct answerID) > 1

See SQL Fiddle with Demo

Or even:

select instanceid
from yourtable
where answerid in (20, 25) -- list of values here
group by instanceid
having count(distinct answerID) = 2 -- match the count of the values here

See SQL Fiddle with Demo