Two MySQL query results are different, but shouldn't be To the best of my knowledge, these results (especially the data in the 'destination' field) should be the same, but I can't find out why they're different:

mysql&gt; select * from cc_did_destination where id_cc_did=1988\G
*************************** 1. row ***************************
            id: 2256
   destination: SIP/t564/12505551234
      priority: 1
    id_cc_card: 2157
     id_cc_did: 1988
  creationdate: 2012-01-31 07:59:01
     activated: 1
secondusedreal: 0
     voip_call: 1
     validated: 1
1 row in set (0.00 sec)

mysql&gt; SELECT cc_did.did, cc_did.id, cc_did_destination.destination     FROM cc_did, cc_did_destination  WHERE cc_did.iduser='2157' AND cc_did_destination.id_cc_card=cc_did.id\G
*************************** 1. row ***************************
        did: 7805551234
         id: 1988
destination: SIP/someuser
*************************** 2. row ***************************
        did: 6045551234
         id: 1997
destination: SIP/macaddress-1
2 rows in set (0.01 sec)


In fact, the data for the 'destination' field is correct in the first select statement. The data in the second query is old and should have been replaced with the data we see in the first query.

As per Rachel below, what I'm trying to do is this; Join this table:

mysql&gt; SELECT destination, id_cc_card, id_cc_did FROM cc_did_destination where id_cc_card=2157;
+----------------------+------------+-----------+
| destination          | id_cc_card | id_cc_did |
+----------------------+------------+-----------+
| SIP/t564/12505551234 |       2157 |      1988 |
| SIP/testuser         |       2157 |      1997 |
+----------------------+------------+-----------+
2 rows in set (0.00 sec)


To this table:

mysql&gt; select did from cc_did where id=1988;
+------------+
| did        |
+------------+
| 7805553315 |
+------------+
1 row in set (0.00 sec)


Except when I try to do that with a JOIN statement, I get this instead:

mysql&gt; SELECT destination, id_cc_card, did FROM cc_did_destination as A join cc_did on A.id_cc_card=cc_did.iduser WHERE A.id_cc_card=2157;
+----------------------+------------+------------+
| destination          | id_cc_card | did        |
+----------------------+------------+------------+
| SIP/t564/12505551234 |       2157 | 6045553939 |
| SIP/testuser         |       2157 | 6045553939 |
| SIP/t564/12505551234 |       2157 | 7805553315 |
| SIP/testuser         |       2157 | 7805553315 |
+----------------------+------------+------------+
4 rows in set (0.01 sec)


Which makes even less sense!

UPDATE: 
I found the problem, and it's all about matching the wrong fields. It should be:

WHERE cc_did.id=cc_did_destination.id_cc_did;


instead of:

WHERE cc_did.id=cc_did_destination.id_cc_card;
Here's a simpler way of looking at your queries

select * 
from A
where A.did = 1988

-- returns record where card = 2157


and

select * 
from B join A on A.card = B.id
where B.userid = 2157 


Since you want the record where a.card = 2157 and a.card = b.id then either


Change your where statement so it is looking for b.id = 2157 or a.card = 2157
Or change your join so you're joining a.card = b.userid