Is it common to create a new case class for join tables?

Question

I have 2 tables like:

users
id
name

lists
-id
-name

user_lists
id
list_id
user_id

So I currently have a query that returns:

def getUsersByList(int listId): Future[Seq[UserList]] = {
  db.run( userLists.filter(f => f.listId === listId) )
}

Now I need to join with the User table in order to get the User fields.

What options do I have in what I return? I guess I have to create a new case class and map to the fields somehow?

Answer 1

I think that your question (though maybe I am wrong) doesn't actually refer only to case class by rather to case class (aka unpacked type ) and table mapping (aka mixed type ). Also it is important to understand that Slick won't help you in any way with one-to-many / many-to-many relationships (it's not an ORM). Here a little bit more: https://stackoverflow.com/a/42218139/2239369

Long story short - your join table is table as any other. The general straightforward answer is: yes . Just create one more case class and table definition .

You for sure need your join table definition (in short - this class that inherits from Slick s Table type - mixed type ). Otherwise you wouldn't be able to generate appropriate query. You could probably go away from creating case class - but I am not sure if it is worth doing it - after all it's one additional line, right? ( case class UserList(id: Id, listId: Id, userId: Id) - or something close to this).

It's perhaps worth to mention that you can also go away from all of above by creating a view on DB level.