I have this classifieds website, and I have about 7 tables in MySql where all data is stored. I have one main table, called "classifieds".

In the classifieds table, there is a column called classified_id. This is not the PK, or a key whatsoever. It is just a number which is used for me to JOIN table records together.

Ex:

 classifieds table:           fordon table:
       id => 33                   id => 12
classified_id => 10             classified_id => 10
  ad_id => 'bmw_m3_92923'           

This above is linked together by the classified_id column.

Now to the Q, I use this method to fetch all records WHERE the column ad_id matches any of the values inside an array, called in this case $ad_arr:

SELECT mt.*, fordon.*, boende.*, elektronik.*, business.*, hem_inredning.*, hobby.*
    FROM classified mt
    LEFT JOIN fordon ON fordon.classified_id = mt.classified_id
    LEFT JOIN boende ON boende.classified_id = mt.classified_id
    LEFT JOIN elektronik ON elektronik.classified_id = mt.classified_id
    LEFT JOIN business ON business.classified_id = mt.classified_id
    LEFT JOIN hem_inredning ON hem_inredning.classified_id = mt.classified_id
    LEFT JOIN hobby ON hobby.classified_id = mt.classified_id 
    WHERE mt.ad_id IN ('$ad_arr')";

Is this good or would this actually fetch unnecessary information?

Check out this Q I posted couple of days ago. In the comments HLGEM is commenting that it is wrong etc etc. What do you think?

http://stackoverflow.com/questions/2782275/another-rookie-question-how-to-implement-count-here

Thanks