- allow exists(s.as_scalar()) to work

2 files changed, 11 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py
index bf3d16e69..5f17c223c 100644
--- a/lib/sqlalchemy/sql/expression.py
+++ b/lib/sqlalchemy/sql/expression.py
@@ -2680,7 +2680,7 @@ class _Exists(_UnaryExpression):
     _from_objects = []
 
     def __init__(self, *args, **kwargs):
-        if args and isinstance(args[0], _SelectBaseMixin):
+        if args and isinstance(args[0], (_SelectBaseMixin, _ScalarSelect)):
             s = args[0]
         else:
             if not args:
diff --git a/test/sql/test_select.py b/test/sql/test_select.py
index d5ba8fa9e..8390c7342 100644
--- a/test/sql/test_select.py
+++ b/test/sql/test_select.py
@@ -279,6 +279,16 @@ sq.myothertable_othername AS sq_myothertable_othername FROM (" + sqstring + ") A
         self.assert_compile(s, "SELECT t.a WHERE t.a = t2.d")
         
     def test_exists(self):
+        s = select([table1.c.myid]).where(table1.c.myid==5)
+        
+        self.assert_compile(exists(s), 
+                    "EXISTS (SELECT mytable.myid FROM mytable WHERE mytable.myid = :myid_1)"
+                )
+        
+        self.assert_compile(exists(s.as_scalar()), 
+                    "EXISTS (SELECT mytable.myid FROM mytable WHERE mytable.myid = :myid_1)"
+                )
+        
         self.assert_compile(exists([table1.c.myid], table1.c.myid==5).select(), "SELECT EXISTS (SELECT mytable.myid FROM mytable WHERE mytable.myid = :myid_1)", params={'mytable_myid':5})
 
         self.assert_compile(select([table1, exists([1], from_obj=table2)]), "SELECT mytable.myid, mytable.name, mytable.description, EXISTS (SELECT 1 FROM myothertable) FROM mytable", params={})