Question

I have a products table…

alt text http://img357.imageshack.us/img357/6393/productscx5.gif

and a revisions table, which is supposed to track changes to product info

alt text http://img124.imageshack.us/img124/1139/revisionslz5.gif

I try to query the database for all products, with their most recent revision…

select * from `products` as `p` left join `revisions` as `r` on `r`.`product_id` = `p`.`product_id` group by `p`.`product_id` order by `r`.`modified` desc 

but I always just get the first revision. I need to do this in one select (ie no sub queries). I can manage it in mssql, is this even possible in mysql?

Answer 1

Here’s how I’d do it:

SELECT p.*, r.* FROM products AS p   JOIN revisions AS r USING (product_id)   LEFT OUTER JOIN revisions AS r2      ON (r.product_id = r2.product_id AND r.modified < r2.modified) WHERE r2.revision_id IS NULL; 

In other words: find the revision for which no other revision exists with the same product_id and a greater modified value.