![]() ![]() If you’re constructing SQL like strftime('%W', 'date') and need a template ¶Ī class attribute, as a format string, that describes the SQL that is Specifically, the function will be interpolated as the function The Func API is as follows: class Func( * expressions, ** extra) ¶ function ¶Ī class attribute describing the function that will be generated. See Database Functions for a list of built-in database functions. need_chairs = GreaterThan ( F ( "num_employees" ), F ( "num_chairs" )). filter ( GreaterThan ( F ( "num_employees" ), F ( "num_chairs" ))) # or annotations. ) # Lookup expressions can also be used directly in filters > Company. filter ( company = OuterRef ( "pk" ), salary_gt = 10 )). > from django.db.models import Exists > Company. order_by ( "name_length" ) # Boolean expression can be used directly in filters. > from django.db.models import CharField > from django.db.models.functions import Length > CharField. desc ()) # or using the double underscore lookup syntax. annotate ( num_offerings = Count ( F ( "products" ) + F ( "services" ))) # Expressions can also be used in order_by(), either directly > Company. annotate ( num_products = Count ( F ( "products" ))) # Aggregates can contain complex computations also > Company. annotate ( num_products = Count ( "products" )) > Company. ticker 'GOOG' # Annotate models with an aggregated value. create ( name = "Google", ticker = Upper ( Value ( "goog" ))) # Be sure to refresh it if you need to access the field. chairs_needed 70 # Create a new company using expressions. ![]() annotate ( chairs_needed = F ( "num_employees" ) - F ( "num_chairs" )). filter ( num_employees_gt = F ( "num_chairs" )). filter ( num_employees_gt = F ( "num_chairs" ) + F ( "num_chairs" )) # How many chairs are needed for each company to seat all employees? > company = (. filter ( num_employees_gt = F ( "num_chairs" ) * 2 ) > Company. filter ( num_employees_gt = F ( "num_chairs" )) # Find companies that have at least twice as many employees # as chairs. from django.db.models import Count, F, Value > from django.db.models.functions import Length, Upper > from django.db.models.lookups import GreaterThan # Find companies that have more employees than chairs. ![]()
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