Er, where is it you're not supposed to use .c? The code in MikeB's
example seems to have .c in every possible location. How do you
access a column without .c?
On 8/10/07, Jeronimo <[EMAIL PROTECTED]> wrote:
>
> Excelent ! It works perfectly !!
> Thank you very much Michael. I was going crazy trying to figure how to
> move
> subquery to the from clause.
>
>
>
> On Aug 9, 8:06 pm, Michael Bayer <[EMAIL PROTECTED]> wrote:
> > OK sorry, i didn't look carefully enough. when you use a scalar
> > subquery, you shouldn't access the "c" attribute on it. I hadn't
> > really realized that and maybe i should add an exception for that.
> > when you access the "c" attribute, you're treating it like another
> > relation to be selected from, so it gets stuck into the from clause.
> > but here, its really just a column expression; so you don't join
> > against one of the subqueries' columns, the subquery IS the thing to
> > be compared against. so heres the full testcase:
> >
> > """
> > create table node(id integer, parent_id integer, type_id integer);
> > insert into node(1,NULL,1);
> > insert into node values(1,NULL,1);
> > insert into node values(2,1,1);
> > insert into node values(3,1,2);
> > insert into node values(4,1,1);
> >
> > SELECT node.id, node.parent_id, node.type_id
> > FROM node
> > WHERE node.id = (SELECT max(n1.id) FROM node AS n1 WHERE n1.type_id =
> > node.type_id);
> >
> > """
> > from sqlalchemy import *
> >
> > meta = MetaData()
> >
> > node_table = Table('nodes', meta,
> > Column('id', Integer),
> > Column('parent_id', Integer),
> > Column('type_id', Integer),
> >
> > )
> >
> > meta.bind = create_engine('sqlite://', echo=True)
> > meta.create_all()
> >
> > node_table.insert().execute(id=1, type_id=1)
> > node_table.insert().execute(id=1, type_id=1)
> > node_table.insert().execute(id=2, parent_id=1, type_id=1)
> > node_table.insert().execute(id=2, parent_id=1, type_id=1)
> > node_table.insert().execute(id=3, parent_id=1, type_id=2)
> > node_table.insert().execute(id=4, parent_id=1, type_id=1)
> >
> > n1 = node_table.alias('n1')
> > sub_query = select([func.max(n1.c.id)],
> > (node_table.c.type_id==n1.c.type_id), scalar=True)
> >
> > print
> > node_table.select(node_table.c.id==sub_query).execute().fetchall()
>
>
> >
>
--
Mike Orr <[EMAIL PROTECTED]>
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