Rails: Order with nulls last

I’m no expert at SQL, but why not just sort by if something is null first then sort by how you wanted to sort it.

Photo.order('collection_id IS NULL, collection_id DESC')  # Null's last
Photo.order('collection_id IS NOT NULL, collection_id DESC') # Null's first

If you are only using PostgreSQL, you can also do this

Photo.order('collection_id DESC NULLS LAST')  #Null's Last
Photo.order('collection_id DESC NULLS FIRST') #Null's First

If you want something universal (like you’re using the same query across several databases, you can use (courtesy of @philT)

Photo.order('CASE WHEN collection_id IS NULL THEN 1 ELSE 0 END, collection_id')

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