Question

Let’s assume I have a database with two tables: categories and articles. Every article belongs to a category.

Now, let’s assume I want to fetch the latest article of each category that fits a specific criteria (read: the article does). If it weren’t for that extra criteria, I could just add a column called last_article_id or something similar to the categories table – even though that wouldn’t be properly normalized.

How can I do this though? I assume there’s something using GROUP BY and HAVING?

Answer 1

Try with:

   SELECT * 
     FROM categories AS c
LEFT JOIN (SELECT * FROM articles ORDER BY id DESC) AS a
       ON c.id = a.id_category
      AND /criterias about joining/
    WHERE /more criterias/
 GROUP BY c.id