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(Teams.Id).label("CustomCount"), Teams.subject).group_by(Teams.subject) for instance in rs: print("Count: ", instance.CustomCount) print("subject: ", instance.subject) print("---------")
You can also execute COUNT using the session object's execute() method:
rs = session.execute(Teams_table.select().with_only_columns([func.count(Teams_table.c.Id).label("CustomCount"), Teams_table.c.subject])group_by(Teams_table.c.subject)) 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(Teams.Reminder).label("CustomSum"), Teams.subject).group_by(Teams.subject) for instance in rs: print("Sum: ", instance.CustomSum) print("subject: ", instance.subject) print("---------")
You can also invoke SUM using the session object's execute() method.
rs = session.execute(Teams_table.select().with_only_columns([func.sum(Teams_table.c.Reminder).label("CustomSum"), Teams_table.c.subject]).group_by(Teams_table.c.subject)) 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(Teams.Reminder).label("CustomAvg"), Teams.subject).group_by(Teams.subject) for instance in rs: print("Avg: ", instance.CustomAvg) print("subject: ", instance.subject) print("---------")
You can also use the session object's execute() method to invoke AVG:
rs = session.execute(Teams_table.select().with_only_columns([func.avg(Teams_table.c.Reminder).label("CustomAvg"), Teams_table.c.subject]).group_by(Teams_table.c.subject)) 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(Teams.Reminder).label("CustomMax"), func.min(Teams.Reminder).label("CustomMin"), Teams.subject).group_by(Teams.subject) for instance in rs: print("Max: ", instance.CustomMax) print("Min: ", instance.CustomMin) print("subject: ", instance.subject) print("---------")
You can also use the session object's execute() method to invoke MAX and MIN:
rs = session.execute(Teams_table.select().with_only_columns([func.max(Teams_table.c.Reminder).label("CustomMax"), func.min(Teams_table.c.Reminder).label("CustomMin"), Teams_table.c.subject]).group_by(Teams_table.c.subject)) for instance in rs: