Sqlalchemy: subquery in FROM must have an alias

Question

How can I structure this sqlalchemy query so that it does the right thing?

I\'ve given everything I can think of an alias, but I\'m still getting:

Pr         


        

Answer 1

You are almost there. Make a "selectable" subquery and join it with the main query via join():

foo_max_time_q = select([func.max(Foo.time).label('foo_max_time'),
                         Foo.id.label('foo_id')
                        ]).group_by(Foo.id
                         ).alias("foo_max_time_q")

foo_q = session.query(
          Foo.id.label('foo_id'),
          Foo.version.label('foo_version'),
          Foo.revision.label('foo_revision'),
          foo_max_time_q.c.foo_max_time.label('foo_max_time')
                ).join(foo_max_time_q, 
                       foo_max_time_q.c.foo_id == Foo.id)

print(foo_q.__str__())

Prints (prettified manually):

SELECT 
    foo.id AS foo_id, 
    foo.version AS foo_version, 
    foo.revision AS foo_revision, 
    foo_max_time_q.foo_max_time AS foo_max_time 
FROM 
    foo 
JOIN 
    (SELECT 
         max(foo.time) AS foo_max_time, 
         foo.id AS foo_id 
     FROM 
         foo 
     GROUP BY foo.id) AS foo_max_time_q 
ON 
    foo_max_time_q.foo_id = foo.id

The complete working code is available in this gist.