SQLAlchemy Group By With Full Child Objects

Question

Imagine the following Media table:

| site       | show_id | time |
| ---------------------|-------|
| CNN        | 1       | \'a\'   |
| ABC        | 2               


        

Answer 1

In SQL the GROUP BY clause condenses the grouped rows into a single row, based on the grouping expressions. My guess is that you are using SQLite, or an older version of MySQL, since you are allowed to select non-aggregates without them being functionally dependent on the grouping expressions. The results contain values from an unspecified row per group in that case, which is seldom — if ever — useful.

A solution is to ORDER BY instead of GROUP BY in SQL and then group in Python based on the order expressions:

from itertools import groupby
from operator import attrgetter

listings = session.query(Media).\
    filter(Media.site == "CNN").\
    order_by(Media.show_id).\
    all()

# Materialize the subiterators to lists
listings = [list(g) for k, g in groupby(listings, attrgetter('show_id'))]