Question

Hey guys need some more help

I have 3 tables USERS, PROFILEINTERESTS and INTERESTS

profile interests has the two foreign keys which link users and interests, they are just done by ID.

I have this so far

$statement = "SELECT
  InterestID
FROM
  `ProfileInterests`
WHERE
  userID = '$profile'";

Now I want it so that it selects from Interests where what it gets from that query is the result.

So say that gives out 3 numbers

1
3
4

I want it to search the Interests table where ID is = to those…I just don’t know how to physically write it in PHP…

Please help.

Answer 1

Using a JOIN:

Best option if you need values from the PROFILEINTERESTS table.

SELECT DISTINCT i.*
  FROM INTERESTS i
  JOIN PROFILEINTERESTS pi ON pi.interests_id = i.interests_id
 WHERE pi.userid = $profileid

Using EXISTS:

SELECT i.*
  FROM INTERESTS i
 WHERE EXISTS (SELECT NULL 
                 FROM PROFILEINTERESTS pi 
                WHERE pi.interests_id = i.interests_id
                  AND pi.userid = $profileid)

Using IN:

SELECT i.*
  FROM INTERESTS i
 WHERE i.interests_id IN (SELECT pi.interests_id
                            FROM PROFILEINTERESTS pi 
                           WHERE pi.userid = $profileid)