RE: SQL Syntax

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Thanks. That was my first attempt, too. Only this will throw out rows, that meet only one of the conditions, too. For example, I would get all pictures that are bigger than 100, regardless of type, and all pictures that are of type jpg, no matter the size. 

Doing it with a view would be an option, but that would immensely decrease flexibility.  

I guess I have to keep on cooking my brain on this ;-) 

I think I did it before, a few years ago when MySQL didn't support views yet, but I can't find that stuff ... 

@Dan: Thanks for forwarding my mail to the MySQL List!

Regards,
Jan


From: Ashley Sheridan [mailto:ash@xxxxxxxxxxxxxxxxxxxx] 
Sent: Wednesday, June 16, 2010 3:09 AM
To: Jan Reiter
Cc: php-general@xxxxxxxxxxxxx
Subject: Re:  SQL Syntax

On Wed, 2010-06-16 at 02:58 +0200, Jan Reiter wrote: 

Hi folks!

I'm kind of ashamed to ask a question, as I haven't followed this list very
much lately. 

 

This isn't exactly a PHP question, but since mysql is the most popular
database engine used with php, I figured someone here might have an idea.

 

I have 2 tables. Table A containing 2 fields. A user ID and a picture ID =>
A(uid,pid) and another table B, containing 3 fields. The picture ID, an
attribute ID and a value for that attribute => B(pid,aid,value).

 

Table B contains several rows for a single PID with various AIDs and values.
Each AID is unique to a PID.  (e.g. AID = 1 always holding the value for the
image size and AID = 3 always holding a value for the image type)

 

The goal is now to join table A on table B using pid, and selecting the rows
based on MULTIPLE  attributes. 

 

So the result should only contain rows for images, that relate to an
attribute ID = 1 (size) that is bigger than 100 AND!!!!!!! an attribute ID =
5 that equals 'jpg'. 

 

I know that there is an easy solution to this, doing it in one query and I
have the feeling, that I can almost touch it with my fingertips in my mind,
but I can't go that final step, if you know what I mean. AND THAT DRIVES ME
CRAZY!!!!!!

 

I appreciate your thoughts on this.

 

Regards,

Jan


You'll be looking for something like this (untested):

SELECT * FROM a
LEFT JOIN b ON (a.pid = b.pid)
WHERE (b.aid = 1 AND b.value > 100) OR (b.aid = 3 AND b.value = 'jpg')

Obviously instead of the * you may have to change to a list of field names to avoid fieldname collision on the two tables.
Thanks,
Ash
http://www.ashleysheridan.co.uk




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