Question

I need to return a list of product id’s that are…

1. Within a specific category (for example ‘Clothing’)
2. Which have various attributes, such as ‘Red’ or ‘Green’
3. Which are themselves within attribute ‘groups’ such as ‘Color’

I’m getting stuck when I need to select MULTIPLE attribute options within MULTIPLE attribute groups. For example, if I need to return a list of products where Color is ‘blue’ OR ‘red’ AND size is ‘Medium’ OR ‘XXL’.

This is my code:

SELECT `products.id` 
FROM 
`products` , 
`categories` ,
`attributes` att1, 
`attributes` att2   
WHERE products.id = categories.productid 
AND `categories.id` = 3 
AND att1.productid = products.id
AND att1.productid = att2.productid
AND 
(att1.attributeid = 58 OR att1.attributeid = 60)
AND 
(att2.attributeid = 12 OR att2.attributeid = 9)

I believe this code works, but It looks pretty messy and I’m not sure my ‘dirty’ self-join is the correct way to go. Has anyone got any ideas on a more ‘elegant’ solution to my problem?

Answer 1

Please use the modern join syntax:

SELECT products.id
FROM products 
join categories on products.id = categories.productid
join attributes att1 on att1.productid = products.id 
join attributes att2 on att1.productid = att2.productid
WHERE categories.id = 3 
AND att1.attributeid IN (58, 60)
AND att2.attributeid IN (12, 9)

It’s easier to read because it clearly demarques join conditions from row filtering conditions. It’s also easier for the SQL optimizer to identify these distinctions and create better query plans

Edited

I alsp added the use of IN (...). Not only does it look nicer, the DB wil use an index with IN but usually not with OR, even though they mean the same thing