diff --git a/clickhouse_orm/query.py b/clickhouse_orm/query.py
index 7287350..e0ab42e 100644
--- a/clickhouse_orm/query.py
+++ b/clickhouse_orm/query.py
@@ -209,21 +209,18 @@ class Q(object):
         Checks if there are any conditions in Q object
         Returns: Boolean
         """
-        return not bool(self._conds or self._children)
+        return not (self._conds or self._children)
 
     @classmethod
     def _construct_from(cls, l_child, r_child, mode):
-        if mode == l_child._mode:
+        if mode == l_child._mode and not l_child._negate:
             q = deepcopy(l_child)
             q._children.append(deepcopy(r_child))
-        elif mode == r_child._mode:
-            q = deepcopy(r_child)
-            q._children.append(deepcopy(l_child))
+
         else:
-            # Different modes
             q = cls()
             q._children = [l_child, r_child]
-            q._mode = mode  # AND/OR
+            q._mode = mode
 
         return q
 
diff --git a/tests/test_querysets.py b/tests/test_querysets.py
index 575435e..10ec863 100644
--- a/tests/test_querysets.py
+++ b/tests/test_querysets.py
@@ -6,7 +6,7 @@ from logging import getLogger
 
 from clickhouse_orm.database import Database
 from clickhouse_orm.engines import CollapsingMergeTree, Memory, MergeTree
-from clickhouse_orm.fields import DateField, DateTimeField, Enum8Field, Int8Field, Int32Field, UInt64Field
+from clickhouse_orm.fields import DateField, DateTimeField, Enum8Field, Int8Field, Int32Field, StringField, UInt64Field
 from clickhouse_orm.funcs import F
 from clickhouse_orm.models import Model
 from clickhouse_orm.query import Q
@@ -568,10 +568,22 @@ class AggregateTestCase(TestCaseWithData):
         limited_qs = qs.limit_by((6, 3), "height")
         self.assertEqual([p.first_name for p in limited_qs[:3]], ["Norman", "Octavius", "Oliver"])
 
+    def test_boolean_logic(self):
+        p = ~Q(x="eggs")
+        q = Q(y="spam")
+        r = p & q
+
+        self.assertEqual(r.to_sql(StringyModel), "(NOT (x = 'eggs')) AND (y = 'spam')")
+
 
 Color = Enum("Color", u"red blue green yellow brown white black")
 
 
+class StringyModel(Model):
+    x = StringField()
+    y = StringField()
+
+
 class SampleModel(Model):
 
     timestamp = DateTimeField()