Question

I’m trying to query 2 tables where the first table will return 1 row and the second table will return multiple rows. So basically the first table with return text on a page and the second table will return a list that will go within the page. Both tables have a reference row which is what both tables are queried on. (See Below)

SELECT shop_rigs.*, shop_rigs_images.*, shop_rigs_parts.*
    FROM shop_rigs
    LEFT JOIN shop_rigs_images 
        ON shop_rigs.shoprigs_ref = shop_rigs_images.shoprigsimg_ref 
    LEFT JOIN shop_rigs_parts
        ON shop_rigs.shoprigs_ref = shop_rigs_parts.shoprigsparts_ref 
    WHERE shoprigs_enabled='1' AND shoprigs_ref='$rig_select'
    ORDER BY shoprigs_order ASC

Is it better to just do 2 queries?

Thanks,

• dane

Answer 1

I would do this in two queries. The problem isn’t efficiency or the size of the respective tables, the problem is that you’re create a Cartesian product between shop_rigs_images and shop_rigs_parts.

Meaning that if a given row of shop_rigs has three images and four parts, you’ll get back 3×4 = 12 rows for that single shop_rig.

So here’s how I’d write it:

SELECT ...
FROM shop_rigs
INNER JOIN shop_rigs_images 
    ON shop_rigs.shoprigs_ref = shop_rigs_images.shoprigsimg_ref 
WHERE shoprigs_enabled='1' AND shoprigs_ref='$rig_select'
ORDER BY shoprigs_order ASC

SELECT ...
FROM shop_rigs
INNER JOIN shop_rigs_parts
    ON shop_rigs.shoprigs_ref = shop_rigs_parts.shoprigsparts_ref 
WHERE shoprigs_enabled='1' AND shoprigs_ref='$rig_select'
ORDER BY shoprigs_order ASC

I left the select-list of columns out, because I agree with @Doug Kress that you should select only the columns you need from a given query, not all columns with *.