Aggregate Functions
Certain aggregate functions can also be used within SQLAlchemy by using the func module. First, you will need to import it:
from sqlalchemy.sql import func
Once imported, the following aggregate functions are available:
COUNT
This example counts the number of records in a set of groups using the session object's query() method.
rs = session.query(func.count(Sheet.RowId).label("CustomCount"), Sheet.RowId).group_by(Sheet.RowId)
for instance in rs:
print("Count: ", instance.CustomCount)
print("RowId: ", instance.RowId)
print("---------")
Alternatively, you can execute COUNT using the session object's execute() method.
rs = session.execute(Sheet_table.select().with_only_columns([func.count(Sheet_table.c.RowId).label("CustomCount"), Sheet_table.c.RowId])group_by(Sheet_table.c.RowId))
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(Sheet.AnnualRevenue).label("CustomSum"), Sheet.RowId).group_by(Sheet.RowId)
for instance in rs:
print("Sum: ", instance.CustomSum)
print("RowId: ", instance.RowId)
print("---------")
Alternatively, you can invoke SUM using the session object's execute() method.
rs = session.execute(Sheet_table.select().with_only_columns([func.sum(Sheet_table.c.AnnualRevenue).label("CustomSum"), Sheet_table.c.RowId]).group_by(Sheet_table.c.RowId))
for instance in rs:
AVG
This example calculates the average amount of a numeric column in a set of groups using the session object's query() method.
rs = session.query(func.avg(Sheet.AnnualRevenue).label("CustomAvg"), Sheet.RowId).group_by(Sheet.RowId)
for instance in rs:
print("Avg: ", instance.CustomAvg)
print("RowId: ", instance.RowId)
print("---------")
Alternatively, you can invoke AVG using the session object's execute() method.
rs = session.execute(Sheet_table.select().with_only_columns([func.avg(Sheet_table.c.AnnualRevenue).label("CustomAvg"), Sheet_table.c.RowId]).group_by(Sheet_table.c.RowId))
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(Sheet.AnnualRevenue).label("CustomMax"), func.min(Sheet.AnnualRevenue).label("CustomMin"), Sheet.RowId).group_by(Sheet.RowId)
for instance in rs:
print("Max: ", instance.CustomMax)
print("Min: ", instance.CustomMin)
print("RowId: ", instance.RowId)
print("---------")
Alternatively, you can invoke MAX and MIN using the session object's execute() method.
rs = session.execute(Sheet_table.select().with_only_columns([func.max(Sheet_table.c.AnnualRevenue).label("CustomMax"), func.min(Sheet_table.c.AnnualRevenue).label("CustomMin"), Sheet_table.c.RowId]).group_by(Sheet_table.c.RowId))
for instance in rs: