Rails Active Record join query

Question

help my with next question:

I have table brands and table products ( has_many - belongs_to association )

in table products i have field "Rank".

And i want to display top5 brands whose total rank of its products - greatest

I try to:

Brand.joins(:products).order('products.rank DESC').limit(10).uniq!

But that incorrect - thats not a sum of products.rank...

How to relize with sum of product ranks

Milan Köpke · Accepted Answer · 2013-03-13 09:27:51Z

1

You are close, but you missed out on grouping and performing the sum on the grouped objects:

Brand.joins(:products).group("brands.id").order('SUM(products.rank) DESC').limit(5)

edited Mar 13, 2013 at 9:27

answered Feb 28, 2013 at 13:35

Milan Köpke

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2 Comments

Dmytro Vasin Over a year ago

ERROR: column reference "id" is ambiguous // with SQL => SELECT "brands".* FROM "brands" INNER JOIN "products" ON "products"."brand_id" = "brands"."id" GROUP BY id(this id) ORDER BY SUM(products.rank) DESC

Dmytro Vasin Over a year ago

Thanks, it's my fault. my mistake =)

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