Fix: PostgreSQLQueryBuilder returns invalid query with no columns to update #832

pypika/dialects.py

@@ -661,6 +661,9 @@ def get_sql(self, with_alias: bool = False, subquery: bool = False, **kwargs: An
 
         querystring = super(PostgreSQLQueryBuilder, self).get_sql(with_alias, subquery, **kwargs)
 
+        if querystring == '':
+            return ''
+
         querystring += self._on_conflict_sql(**kwargs)
         querystring += self._on_conflict_action_sql(**kwargs)
 

pypika/tests/test_inserts.py

@@ -467,6 +467,11 @@ def test_on_conflict_where_complex(self):
             str(qs),
         )
 
+    def test_on_conflict_no_inserts(self):
+        query = PostgreSQLQuery.into(self.table_abc).on_conflict("id").do_nothing()
+
+        self.assertEqual('', str(query))
+
 
 class PostgresInsertIntoReturningTests(unittest.TestCase):
     table_abc = Table("abc")
@@ -567,6 +572,11 @@ def test_insert_returning_from_other_table(self):
         with self.assertRaises(QueryException):
             PostgreSQLQuery.into(self.table_abc).insert(1).returning(table_cba.id)
 
+    def test_insert_returning_no_inserts(self):
+        query = PostgreSQLQuery.into(self.table_abc).returning(self.table_abc.star)
+
+        self.assertEqual('', str(query))
+
 
 class InsertIntoOnDuplicateTests(unittest.TestCase):
     table_abc = Table("abc")

pypika/tests/test_updates.py

@@ -152,6 +152,11 @@ def test_update_returning_star(self):
 
         self.assertEqual('UPDATE "abc" SET "foo"=\'bar\' WHERE "foo"=0 RETURNING *', str(q))
 
+    def test_update_returning_no_updates(self):
+        q = PostgreSQLQuery.update(self.table_abc).returning(self.table_abc.star)
+
+        self.assertEqual('', str(q))
+
 
 class SQLLiteUpdateTests(unittest.TestCase):
     table_abc = Table("abc")