diff --git a/aiochclient/types.py b/aiochclient/types.py
index 1bafd8d..94db868 100755
--- a/aiochclient/types.py
+++ b/aiochclient/types.py
@@ -1,5 +1,6 @@
 import datetime as dt
 import re
+from abc import ABC, abstractmethod
 from typing import Any, Callable, Generator, Optional
 from uuid import UUID
 
@@ -8,7 +9,7 @@
 __all__ = ["what_py_converter", "rows2ch"]
 
 
-class BaseType:
+class BaseType(ABC):
 
     __slots__ = ("name", "container")
 
@@ -31,9 +32,9 @@ def __init__(self, name: str, container: bool = False):
         self.name = name
         self.container = container
 
+    @abstractmethod
     def p_type(self, string):
         """ Function for implementing specific actions for each type """
-        return string
 
     @classmethod
     def decode(cls, val: bytes) -> str:
diff --git a/tests.py b/tests.py
index d63d1cd..92b5a67 100644
--- a/tests.py
+++ b/tests.py
@@ -404,6 +404,11 @@ async def test_fetchrow_with_empties(self):
             :
         ] == self.rows[1]
 
+    async def test_fetchrow_none_result(self):
+        assert (
+            await self.ch.fetchrow("SELECT * FROM all_types WHERE uint8=42")
+        ) is None
+
     async def test_fetchone_full(self):
         assert (await self.ch.fetchone("SELECT * FROM all_types WHERE uint8=1"))[
             :
@@ -414,6 +419,16 @@ async def test_fetchone_with_empties(self):
             :
         ] == self.rows[1]
 
+    async def test_fetchone_none_result(self):
+        assert (
+            await self.ch.fetchone("SELECT * FROM all_types WHERE uint8=42")
+        ) is None
+
+    async def test_fetchval_none_result(self):
+        assert (
+            await self.ch.fetchval("SELECT uint8 FROM all_types WHERE uint8=42")
+        ) is None
+
     async def test_fetch(self):
         rows = await self.ch.fetch("SELECT * FROM all_types")
         assert [row[:] for row in rows] == self.rows
@@ -428,6 +443,9 @@ async def test_iterate(self):
             row[:] async for row in self.ch.iterate("SELECT * FROM all_types")
         ] == self.rows
 
+    async def test_select_with_execute(self):
+        assert (await self.ch.execute("SELECT * FROM all_types WHERE uint8=1")) is None
+
 
 @pytest.mark.record
 @pytest.mark.usefixtures("class_chclient")
@@ -439,8 +457,9 @@ async def test_common_objects(self):
 
     async def test_lazy_decoding(self):
         record = await self.ch.fetchrow("SELECT * FROM all_types WHERE uint8=2")
-        assert type(record._row[0]) == bytes
+        assert type(record._row) == bytes
         record[0]
+        assert type(record._row) == tuple
         assert type(record._row[0]) == int
 
     async def test_mapping(self):