On May 16, 2007, at 7:51 AM, ml wrote:
>
> Hi!
>
> Example:
> I have a table "pictures" with columns "format", "size", and
> "color". I
> want to get items grouped by "color":
>
> res = session.query(Picture).group_by(Picture.c.color).select()
>
> but PostgreSQL reports that format and size must be in the GROUP BY or
> in a aggregate function (because it doesn't know which values it can
> pick). Can I tell SA that it should apply e.g. MIN() function to all
> columns not included in the GROUP BY?
not directly with an ORM query, since the ORM maps objects to the
individual rows of a selectable, not aggregates of that selectable
(in particular PK here is unclear? is the PK composite of those other
cols or is a surrogate?). youd have to somehow correlate a primary
key value from your MIN query to the straight "Picutre" table, such as:
palias = picture_table.alias('pa')
session.query(Picture).select(exists([1], group_by=[palias.c.color],
having=func.min(palias.c.id)==pictures.c.id))
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