there's a way to get the tuple comparison to work here though it's not as common, I'd have to try it out and there might be some quirks to work out. I would think this would be more straightforward using a straight AND:
and_(mo.c.col1 == myselect.c.col1, mo.c.col2 == myselect.c.col2, mo.c.col3 == myselect.c.col3) where "myselect" is like: select([...]).where(...).alias() On Apr 20, 2014, at 9:33 PM, Rick Otten <rottenwindf...@gmail.com> wrote: > So FWIW, for now, I cast all three columns into strings and concatenated them > using the column_property() expression in the mapper, and then did the > comparison on that. It worked ok to create the join condition I needed. It > wasn't a pretty as a tuple comparison but it got the job done and I can hit > my deadline for tomorrow morning. > > > On Sunday, April 20, 2014 2:38:21 PM UTC-4, Rick Otten wrote: > I would like to apply a condition in an outer join that matches a multi-item > list rather than a single value. > > In other words, I'm trying to get SQLAlchemy 0.8.6 connecting to PostgreSQL > 9.3.4 to generate SQL like this: > > > > select > * > from > mytable mt > left outer join myothertable mo on > (m0.col1, m0.col2, mo.col3) = (select m2.col1, m2.col2, m2.col3 > from myothertable m2 > where mt.col1 = > m2.wilson_id > order by m2.col3 desc > limit 1) > > > > When I construct my query object back in Python 2.7: > > mo = aliased(myothertable) > m2 = aliased(myothertable) > mySession.query(mytable, myothertable)\ > .select_from(mytable)\ > .outerjoin(mo, > [mo.col1, mo.col2, mo.col3] == select(\ > [m2.col1, m2.col2, m2.col3])\ > .where(m2.col1 == mytable.col1)\ > .order_by(m2.col3.desc())\ > .limit(1)) > > > I get: > > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 1699, in > outerjoin > File "<string>", line 1, in <lambda> > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 51, in > generate > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 1816, in > _join > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 1846, in > _join_left_to_right > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 1861, in > _prepare_right_side > File "build/bdist.linux-x86_64/egg/sqlalchemy/inspection.py", line 74, in > inspect > sqlalchemy.exc.NoInspectionAvailable: No inspection system is available for > object of type <type 'bool'> > > I tried both List type and Tuple type in my comparison from the inner select > statement. > When I look at the code where this exception is thrown, it suggests that > something is wrong with my mapping. > > I've done this join by comparing a single column with these two tables, and > I've done similar things with other single column comparisons. I'm not sure > why I'm unable to compare a set of columns instead. > > I've been pondering casting all three columns to string and then > concatenating them (either in the table mapping, or in the query) to see if I > can get back to a single value comparision which I expect to work. I'd > rather just compare the tuple/lists though. > > I could use some hints. If you guys have some. Thanks! > > > > > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at http://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
