How to use avg and sum in SQLAlchemy query

Question

I\'m trying to return a totals/averages row from my dataset which contains the SUM of certain fields and the AVG of others.

I could do this in SQL via:

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Answer 1

ttention = Attention_scores.query.with_entities(func.avg(Attention_scores.score)).filter(classroom_number == classroom_number).all()

i tried like this . it gave the correct average

Answer 2

You cannot use MyObject.query here, because SqlAlchemy tries to find a field to put result of avg function to, and it fails.

This isn't exactly true. func.avg(Rating.field2).label('average') returns a Column object (the same type object that it was given to be precise). So you can use it with the with_entities method of the query object.

This is how you would do it for your example:

Rating.query.with_entities(func.avg(Rating.field2).label('average')).filter(Rating.url == url_string.netloc)

Answer 3

You should use something like:

from sqlalchemy.sql import func
session.query(func.avg(Rating.field2).label('average')).filter(Rating.url==url_string.netloc)

You cannot use MyObject.query here, because SqlAlchemy tries to find a field to put result of avg function to, and it fails.