add support for boolean aggregates (#332)

Author: mShan0

mssql/functions.py

@@ -32,6 +32,16 @@
 class TryCast(Cast):
     function = 'TRY_CAST'
 
+def sqlserver_cast(self, compiler, connection, **extra_context):
+    if hasattr(self.source_expressions[0], 'lookup_name'):
+        if self.source_expressions[0].lookup_name in ['gt', 'gte', 'lt', 'lte']:
+            return self.as_sql(
+                compiler, connection,
+                template = 'CASE WHEN %(expressions)s THEN 1 ELSE 0 END',
+                **extra_context
+            )
+    return self.as_sql(compiler, connection, **extra_context)
+    
 
 def sqlserver_atan2(self, compiler, connection, **extra_context):
     return self.as_sql(compiler, connection, function='ATN2', **extra_context)
@@ -451,6 +461,7 @@ def sqlserver_sha512(self, compiler, connection, **extra_context):
     key_transform_exact_process_rhs = KeyTransformExact.process_rhs
     KeyTransformExact.process_rhs = json_KeyTransformExact_process_rhs
     HasKeyLookup.as_microsoft = json_HasKeyLookup
+Cast.as_microsoft = sqlserver_cast
 Degrees.as_microsoft = sqlserver_degrees
 Radians.as_microsoft = sqlserver_radians
 Power.as_microsoft = sqlserver_power