SQL: Introducing Having
I was asked recently to write the SQL needed to define a class method named User.busy? that would return an array of User records with a post count greater than or equal to 2.
Let's assume we have two tables, users and posts, linked by the primary key users.id and the foreign key posts.user_id.
I knew high level that I would need a join between the two tables and some way to apply a where clause on the count of posts grouped by users. A quick bit of research introduced me to the group by plus having technique.
1 select users.* from users join posts on posts.user_id = users.id group by posts.user_id having count(*) >= 2Ta da!
Looking forward to the cooler weather of Fall. It is blazing hot! I had two lobster rolls the other day that made me think of you. Always welcome to come up to NYC! Love you.
by Eric on SQL: Introducing Having