Question

I need some help figuring out a query

I have 3 tables

sources
id, name, rank

origin
id, source_id (FK to sources id), name

One source can have many origins

product
id, origin_id (FK to origin id), name, time_added

One origin can have many products

Now, what I want is to select the most recent products per source, ordered by rank descending

Any suggestions?

Answer 1

This should do as you have requested, though without sample output it’s hard to be 100% certain. Inner query selects products linked to the source id ordered by the date added from newest to oldest, and in turn that’s joined to sources and grouped.

SELECT
  *
FROM sources AS s
INNER JOIN (
    SELECT 
        origins.source_id,
        product.*
     FROM origin
     INNER JOIN product
     ON product.origin_id = origin.origin_id
     ORDER BY time_added DESC
) AS productsOrdered
ON productsOrdered.source_id = sources.source_id

ORDER BY s.rank DESC, productsOrdered.time_added DESC

This avoids having to do potentially expensive opreations as the inner select should be pretty fast and can be limited as required