MySQL: Is a subquery the right move? - php

Question

I have several products each with several images.
I am trying to display 3 products with only 1 of their corresponding images.
With the code below i get 3 different products with only 1 image being successfully displayed.
If i take off the sub-query LIMIT 1 i get 3 of the same product just with different images.
Any help would be greatly appreciated.
SELECT pro.id,
pro.title AS product_title,
pro.price,
img.image,
img.title AS image_title,
FROM products AS pro
LEFT JOIN
(SELECT product_id,image_library_id
FROM images_products
LIMIT 1) AS ips
ON ips.product_id = pro.id
LEFT JOIN image_library AS img
ON img.id = ips.image_library_id
WHERE pro.status_id='1'
LIMIT 3

Answer 1

Your question-title mentions a "correlated subquery", but this actually isn't a correlated subquery; it's a regular (uncorrelated) subquery that you're joining to. So that subquery is performed first, before the join, and only returns one record from images_products at all. You'd therefore get at most one working image. I believe that the query you want is this:
SELECT pro.id,
pro.title AS product_title,
pro.price,
img.image,
img.title AS image_title
FROM products AS pro
LEFT
JOIN image_library AS img
ON img.id =
( SELECT image_library_id
FROM images_products AS ips
WHERE ips.product_id = pro.id
LIMIT 1
)
WHERE pro.status_id = '1'
LIMIT 3
;
using a true correlated subquery. (Tested.)