Question

I am fairly new to php and mysql and am having an issue with a query.

SELECT candidate_id.master_id, candidate_contact_details.first_name,
candidate_contact_details.last_name,
candidate_contact_details.home_phone FROM candidate_id,
candidate_contact_details, qualifications WHERE qualifications.active = 'yes';

The database only has 2 records across 5 tables but this is returning 12 results in both php and directly on the mysql console. I know I am doing something wrong but cannot figure it out.

Answer 1

you need to make the query consistent.
the query you have is the Cartesian product of all your tables which in most of the case doesn’t make much sense

here is something better (assuming that master_id is the reference to a candidate instance):

SELECT candidate_id.master_id, candidate_contact_details.first_name,
candidate_contact_details.last_name,
candidate_contact_details.home_phone
FROM candidate_id, candidate_contact_details, qualifications
WHERE qualifications.active = 'yes' AND candidate_id.master_id = candidate_contact_details.master_id AND qualifications.master_id = candidate_id.master_id;

even better would be use JOIN and use alias for table name to make code more readable:

SELECT c.master_id, cc.first_name,cc.last_name,cc.home_phone
FROM candidate_id c
   JOIN candidate_contact_details cc
     ON c.master_id = cc.master_id
   JOIN qualifications q
     ON c.master_id = q.master_id
WHERE q.active = 'yes';