python - SQLAlchemy convert outer join ORM query to Core -


i'm having problems sqlalchemy's select_from statement when using core component. try construct outer join query looks like:

query = select([b1.c.id, b1.c.num, n1.c.name, n1.c.num, ...]         ).where(and_(             ... conditions ...         )     ).select_from(         ???.outerjoin(         n1,         and_(             ... conditions ...         )     ).select_from(... more outer joins similar above ...)

according docs, structure should this:

table1 = table('t1', column('a')) table2 = table('t2', column('b')) s = select([table1.c.a]).\     select_from(         table1.join(table2, table1.c.a==table2.c.b)     )

my problem don't have table1 object in case, select ... part consists of columns , not single table (see question marks in query). i've tried using n1.outerjoin(n1..., caused exception (exception: (programmingerror) table name "n1" specified more once).

the above snippet derived working session-based (orm) query, try convert (with limited success).

b = table('b', metadata,      column('id', integer, sequence('seq_b_id')),     column('num', integer, nullable=false),     column('active', boolean, default=false), ) n = table('n', metadata,      column('b_id', integer, nullable=false),     column('num', integer, nullable=false),     column('active', boolean, default=false), ) p = table('p', metadata,      column('b_id', integer, nullable=false),     column('num', integer, nullable=false),     column('active', boolean, default=false), )  n1 = aliased(n, name='n1') n2 = aliased(n, name='n2') b1 = aliased(b, name='b1') b2 = aliased(b, name='b2') p1 = aliased(p, name='p1') p2 = aliased(p, name='p2')  result = sess.query(b1.id, b1.num, n1.c.name, n1.c.num, p1.par, p1.num).filter(         b1.active==false,         b1.num==sess.query(func.max(b2.num)).filter(             b2.id==b1.id         )     ).outerjoin(         n1,          and_(             n1.c.b_id==b1.id,             n1.c.num<=num,             n1.c.active==false,             n1.c.num==sess.query(func.max(n2.num)).filter(                 n2.id==n1.c.id             )         )     ).outerjoin(         p1,         and_(             p1.b_id==b1.id,             p1.num<=num,             p1.active==false,             p1.num==sess.query(func.max(p2.num)).filter(                 p2.id==p1.id             )         )     ).order_by(b1.id)

how go converting orm query plain core query? update:

i able narrow down problem. seems combination of 2 select_from calls causes problem.

customer = table('customer', metadata,     column('id', integer),     column('name', string(50)), ) order = table('order', metadata,     column('id', integer),     column('customer_id', integer),     column('order_num', integer), ) address = table('address', metadata,     column('id', integer),     column('customer_id', integer),             column('city', string(50)), ) metadata.create_all(db)  customer1 = aliased(customer, name='customer1') order1 = aliased(order, name='order1') address1 = aliased(address, name='address1')  columns = [     customer1.c.id, customer.c.name,     order1.c.id, order1.c.order_num,      address1.c.id, address1.c.city ] query = select(columns) query = query.select_from(     customer1.outerjoin(         order1,         and_(             order1.c.customer_id==customer1.c.id,         )     ) ) query = query.select_from(     customer1.outerjoin(         address1,         and_(             customer1.c.id==address1.c.customer_id         )     ) )     result = connection.execute(query) r in result.fetchall():     print r

the above code causes following exception:

programmingerror: (programmingerror) table name "customer1" specified more once  'select customer1.id, customer.name, order1.id, order1.order_num, address1.id, address1.city \nfrom customer, customer customer1 left outer join "order" order1 on order1.customer_id = customer1.id, customer customer1 left outer join address address1 on customer1.id = address1.customer_id' {}

if bit more experienced in using sqlalchemy, bug...

i managed solved problem. instead of cascading select_from, additional joins need chained actual join. above query read:

query = select(columns) query = query.select_from(     customer1.outerjoin(         order1,         and_(             order1.c.customer_id==customer1.c.id,         )     ).outerjoin(         address1,         and_(             customer1.c.id==address1.c.customer_id         )     ) )

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