Refs #28643 -- Added NullIf database function.

Thanks Nick Pope, Mariusz Felisiak, and Tim Graham for reviews.

2 files changed, 14 insertions, 3 deletions

diff --git a/django/db/models/functions/__init__.py b/django/db/models/functions/__init__.py
index f005546eb0..2d58821653 100644
--- a/django/db/models/functions/__init__.py
+++ b/django/db/models/functions/__init__.py
@@ -1,4 +1,4 @@
-from .comparison import Cast, Coalesce, Greatest, Least
+from .comparison import Cast, Coalesce, Greatest, Least, NullIf
 from .datetime import (
     Extract, ExtractDay, ExtractHour, ExtractIsoYear, ExtractMinute,
     ExtractMonth, ExtractQuarter, ExtractSecond, ExtractWeek, ExtractWeekDay,
@@ -20,7 +20,7 @@ from .window import (
 
 __all__ = [
     # comparison and conversion
-    'Cast', 'Coalesce', 'Greatest', 'Least',
+    'Cast', 'Coalesce', 'Greatest', 'Least', 'NullIf',
     # datetime
     'Extract', 'ExtractDay', 'ExtractHour', 'ExtractMinute', 'ExtractMonth',
     'ExtractQuarter', 'ExtractSecond', 'ExtractWeek', 'ExtractWeekDay',
diff --git a/django/db/models/functions/comparison.py b/django/db/models/functions/comparison.py
index ff0f0e09d0..6c0b33bdcc 100644
--- a/django/db/models/functions/comparison.py
+++ b/django/db/models/functions/comparison.py
@@ -1,5 +1,5 @@
 """Database functions that do comparisons or type conversions."""
-from django.db.models.expressions import Func
+from django.db.models.expressions import Func, Value
 
 
 class Cast(Func):
@@ -103,3 +103,14 @@ class Least(Func):
     def as_sqlite(self, compiler, connection, **extra_context):
         """Use the MIN function on SQLite."""
         return super().as_sqlite(compiler, connection, function='MIN', **extra_context)
+
+
+class NullIf(Func):
+    function = 'NULLIF'
+    arity = 2
+
+    def as_oracle(self, compiler, connection, **extra_context):
+        expression1 = self.get_source_expressions()[0]
+        if isinstance(expression1, Value) and expression1.value is None:
+            raise ValueError('Oracle does not allow Value(None) for expression1.')
+        return super().as_sql(compiler, connection, **extra_context)