Question

How would I recreate the following query in Rails speak so that it returns the amount of rows processed?

self.connection.execute('DELETE FROM `cd_artist`
LEFT JOIN `cdpedia` ON cd_artist.id = cdpedia.`artistId`
WHERE artistId IS NULL;')

I realize I should use something like Artist.find_by_sql for it to return something, but that gives me an error.

Perhaps there is a more elegant way of doing this?

I want to avoid the Rails way of first searching the database, then grabbing the IDs and deleting the entries with Object.destroy or even Object.delete(id) since a SQL call is so much faster (if you have the right indexes), but I’m curious as to what the “proper” way to do it is.

Answer 1

You just have to replace execute by delete, and it will return the number of rows affected.

self.connection.delete('DELETE FROM `cd_artist`
LEFT JOIN `cdpedia` ON cd_artist.id = cdpedia.`artistId`
WHERE artistId IS NULL;')

There is maybe a more elegant way to do this with ActiveRecord, but I doubt it will be as efficient as a raw SQL query.