On Apr 24, 2007, at 4:05 PM, Chris Shenton wrote:
> Am I being stupid about not seeing the difference -- what keywords and > arguments I can use -- between: > > self.session.query(MyClass).select(...) > > and > > select(...) > > these two methods are fundamentally different. first of all, session.query(MyClass) deals with object relational mapping, and select() deals with result sets...i think you got that part. so the big thing with query(MyClass).select() is that its designed to return object instances. in order to return object instances, the mapper already knows what columns it wants to select...so in the vast majority of usages with query(), you dont specify any "columns" clause, and the "columns" argument, which you know from sqlalchemy.sql.select(), is not part of the select() method on sqlalchemy.orm.query.Query. so the basic answer to your question is, sqlalchemy.sql.select() takes the list of columns as its first argument, query(MyClass).select () does not. in the latter case, the "columns" clause is automatically all of the columns from MyClass' table. there is a "group_by" keyword argument available on query.select(), as well as a generative method group_by() which is used like query.group_by(<list of columns>).select() however, Query() has a whole boatload of new features that came out in 0.3.6. the best way to get a sense for everything that query can do is to look at the generatted docs, which i now have linked from the main docs in two places (ive also recently rewritten the whole documentation on Query, as of last weekend, worth checking out): http://www.sqlalchemy.org/docs/ sqlalchemy_orm_query.html#docstrings_sqlalchemy.orm.query_Query as it turns out, theres a neat way to do exactly what you want with this most recent Query object (the goal being, return object instances plus an aggregate value in one shot). do it like: session.query(Fault).add_column(func.count(Fault.c.severity).label ('count')).group_by([c for c in Fault.c]).filter(Fault.c.ts_created >= self.this_week).list() where session.query(Fault) will in all cases use all of the columns from Fault's table in a SELECT statement, and add_column() adds an extra column along. because you added an external column, the results will be expressed as tuples consisting of the entity and the numerical count. notice also that the word "select()" isnt even in there. the newer style establishes itself as more clearly distinct from the base SQL construction system. the GROUP BY clause there is needed to tell mysql about all the columns that are not part of your aggregate function (the aggregate being the "count" function)...since all the columns from Fault's table will be in the columns clause, you need to add them all to the group by. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
