Aggregate Functions
Certain aggregate functions can also be used within SQLAlchemy by using the func module.
To import this module, execute:
from sqlalchemy.sql import func
Once func is imported, the following aggregate functions are available:
COUNT
The following example counts the number of records in a set of groups using the session object's query() method.rs = session.query(func.count(ItemListing.ItemId).label("CustomCount"), ItemListing.HitCount).group_by(ItemListing.HitCount) for instance in rs: print("Count: ", instance.CustomCount) print("HitCount: ", instance.HitCount) print("---------")
You can also execute COUNT using the session object's execute() method:
rs = session.execute(ItemListing_table.select().with_only_columns([func.count(ItemListing_table.c.ItemId).label("CustomCount"), ItemListing_table.c.HitCount])group_by(ItemListing_table.c.HitCount)) for instance in rs:
SUM
This example calculates the cumulative amount of a numeric column in a set of groups.
rs = session.query(func.sum(ItemListing.MinimumBestOfferPrice).label("CustomSum"), ItemListing.HitCount).group_by(ItemListing.HitCount) for instance in rs: print("Sum: ", instance.CustomSum) print("HitCount: ", instance.HitCount) print("---------")
You can also invoke SUM using the session object's execute() method.
rs = session.execute(ItemListing_table.select().with_only_columns([func.sum(ItemListing_table.c.MinimumBestOfferPrice).label("CustomSum"), ItemListing_table.c.HitCount]).group_by(ItemListing_table.c.HitCount)) for instance in rs:
AVG
This example uses the session object's query() method to calculate the average amount of a numeric column in a set of groups:rs = session.query(func.avg(ItemListing.MinimumBestOfferPrice).label("CustomAvg"), ItemListing.HitCount).group_by(ItemListing.HitCount) for instance in rs: print("Avg: ", instance.CustomAvg) print("HitCount: ", instance.HitCount) print("---------")
You can also use the session object's execute() method to invoke AVG:
rs = session.execute(ItemListing_table.select().with_only_columns([func.avg(ItemListing_table.c.MinimumBestOfferPrice).label("CustomAvg"), ItemListing_table.c.HitCount]).group_by(ItemListing_table.c.HitCount)) for instance in rs:
MAX and MIN
This example finds the maximum value and minimum value of a numeric column in a set of groups.rs = session.query(func.max(ItemListing.MinimumBestOfferPrice).label("CustomMax"), func.min(ItemListing.MinimumBestOfferPrice).label("CustomMin"), ItemListing.HitCount).group_by(ItemListing.HitCount) for instance in rs: print("Max: ", instance.CustomMax) print("Min: ", instance.CustomMin) print("HitCount: ", instance.HitCount) print("---------")
You can also use the session object's execute() method to invoke MAX and MIN:
rs = session.execute(ItemListing_table.select().with_only_columns([func.max(ItemListing_table.c.MinimumBestOfferPrice).label("CustomMax"), func.min(ItemListing_table.c.MinimumBestOfferPrice).label("CustomMin"), ItemListing_table.c.HitCount]).group_by(ItemListing_table.c.HitCount)) for instance in rs: