Greetengs, i tried to solve the problem using different approaches but
none of them worked.
Here are the examples using both, plain SQL and SQLALchemy methods.
* Using plain SQL:
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);
Results:
id | parent_id | type_id
----+-----------+---------
3 | 1 | 2
4 | 1 | 1
(2 rows)
* Using SQLALchemy:
class Node(BaseModel): pass
node_table = Table('node', metadata, Column('id', Integer),
Column('parent_id', Integer), Column('type_id', Integer))
assign_mapper(session.context, Node, node_table)
n1 = node_table.alias('n1')
sub_query = select([func.max(node_table.c.id).label('max_id')],
(node_table.c.type_id==n1.c.type_id)).alias('sub_query')
n1.select(n1.c.id==sub_query.c.max_id).execute().fetchall()
Results:
[(4, 1, 1)]
It seems that sub_query is not using the parent query field
definitions, and instead is redeclaring node_table.
Does someone knows whats happening ? Thanks in advance !
Regards !
Jeronimo
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