My SQL query is returning duplicate results - php

Question

I have an annoying problem that I cannot get past.
I have a photograph database broken up into two tables:
Table 1 (snaps) consists of four columns:
'photoid', 'filename', 'location', 'created'
Table 2 (befter) which displays the photos in pairs consists of
'ppairid', 'beforeid', 'afterid', 'description'
Table 2 displays the photo pairs, as beforeid and afterid use the unique photoid INT from table 1. All quite simple it would seem.
BUT one of the queries that I have come up with (by location) duplicates if the location of beforeid and afterid are the same. So for example:-
SELECT *
FROM befter, snaps
WHERE (snaps.photoid = befter.beforeid OR snaps.photoid = befter.afterid)
AND snaps.location = 'oxford'
is fine when the photo location is different but not if they're the same. I've tried adding DISTINCT etc but I can't figure it out.
Any ideas please?
P

Answer 1

Use two left joins:
select b.*, sb.*, sa.*
from befter b left join
snaps sb
on sb.photoid = b.beforeid and sb.location = 'oxford' left join
snaps sa
on sa.photoid = b.afterid and sa.location = 'oxford'
where sb.photoid is not null or sa.photoid is not null;
This includes both the before and after snaps in the result set.

Answer 2

You have to tell the SQL statement what you are fetching from the given tables. If you take an * on two tables, then you will get duplicate results.
Try this:
SELECT
snaps.photoid, snaps.filename, snaps.location, snaps.created, befter.ppairid,
befter.beforeid, befter.afterid, befter.description
FROM
befter
INNER JOIN
snaps
ON
snaps.photoid = befter.ppairid
WHERE
snaps.location='oxford'
AND
(snaps.photoid = befter.beforeid OR snaps.photoid = befter.afterid)