default null ordering for window functions

Author: Tim Nyborg

mssql/functions.py

@@ -4,10 +4,10 @@
 import json
 
 from django import VERSION
-from django.db.models import BooleanField
+from django.db.models import BooleanField, Value
 from django.db.models.functions import Cast
 from django.db.models.functions.math import ATan2, Log, Ln, Mod, Round
-from django.db.models.expressions import Case, Exists, OrderBy, When
+from django.db.models.expressions import Case, Exists, OrderBy, When, Window
 from django.db.models.lookups import Lookup, In
 from django.db.models import lookups
 
@@ -55,6 +55,13 @@ def sqlserver_round(self, compiler, connection, **extra_context):
     return self.as_sql(compiler, connection, template='%(function)s(%(expressions)s, 0)', **extra_context)
 
 
+def sqlserver_window(self, compiler, connection, template=None):
+    # MSSQL window functions require an OVER clause with ORDER BY
+    if self.order_by is None:
+        self.order_by = Value('SELECT NULL')
+    return self.as_sql(compiler, connection, template)
+
+
 def sqlserver_exists(self, compiler, connection, template=None, **extra_context):
     # MS SQL doesn't allow EXISTS() in the SELECT list, so wrap it with a
     # CASE WHEN expression. Change the template since the When expression
@@ -180,10 +187,12 @@ def json_HasKeyLookup(self, compiler, connection):
 Log.as_microsoft = sqlserver_log
 Mod.as_microsoft = sqlserver_mod
 Round.as_microsoft = sqlserver_round
+Window.as_microsoft = sqlserver_window
 
 if DJANGO3:
     Lookup.as_microsoft = sqlserver_lookup
 else:
     Exists.as_microsoft = sqlserver_exists
 
 OrderBy.as_microsoft = sqlserver_orderby
+