Hey all,
First and foremost, thank you for this wonderful library! This is my first
post to the list and I am very grateful for those who have taken the time
to make sqlalchemy.
I am using SQLalchemy as a backend for an object-oriented language I am
developing. The way it works is that it is developed in python and
SQLalchemy outputs SQL that represents the entire logic of the program.
The ORM has been a great way to do this, but there is one hurdle that I
continue to face in my development strategy: the creation of subqueries
that behave like classes.
For example, if I have a class representing a table:
class Holder(Base) :
id = Column('id', Integer, primary_key=True)
house = Column('house', Integer)
team = Column('team', Integer)
duration_num = Column('duration_num', Integer)
duration_den = Column('duration_num', Integer)
duration = column_property(1 * duration_num / duration_den)
what would be nice is to do something like:
query(Holder.house, Holder.team,
MAX(Holder.duration)).group_by(Holder.house, Holder.team)
where MAX was intelligent enough to expand the query into two queries on
Holder joined to each other: one that found the max of duration and another
that did a join to the original table to get the corresponding num and den.
I discuss this in the stack overflow
post:
http://stackoverflow.com/questions/24257066/sql-legality-of-including-ungrouped-columns-in-group-by-statement.
I've currently been doing this type of joining by hand, but that weds my
abstraction of the column property to its internals. What would be great
is to be able to define aggregate functions on column properties and what
behavior they'd result in. Perhaps this is easy and I've missed how to do
it, but so far I haven't found any good solutions. Any help would be
appreciated!
Cheers,
Mike
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