Question

ownself = db.session.query(User.id.label("user_1_id"), User.id.label("user_id"))

User2 = aliased(User)
FacebookUser2 = aliased(FacebookUser)
friends = (db.session.query(User2.id.label("user_1_id"), User.id.label("user_id")).
           join(FacebookUser2, User2.facebook_info == FacebookUser2.id).
           join(FriendConnection, FacebookUser2.id == FriendConnection.fb_user_from).
           join(FacebookUser, FacebookUser.id == FriendConnection.fb_user_to).
           join(User, User.facebook_info == FacebookUser.id)
           )

u_all = union_all(ownself, friends)

q = (db.session.query(User).filter(u_all.c.user_id == user.id))

I get the error “Every derived table must have its own alias” with MySQL, how can I fix this?

Answer 1

I think the comment in your other question should cover this now: just add .alias("alias_name") to the (partial) query in question.
In your code example, add it to both sub-queries:

# old:
u_all = union_all(ownself, friends)
# new:
u_all = union_all(ownself.alias("subquery1"), friends.alias("subquery2"))