diff --git a/index.php b/index.php
index f30b87b..c9c9199 100644
--- a/index.php
+++ b/index.php
@@ -32,11 +32,7 @@ abstract class BaseModel {
             get_called_class());
     }
     
-    private static function Initialize() {
-        if (self::$sql === null) { 
-            throw new Exception('sql not inited');
-        }
-    }
+    abstract private static function Initialize();
 }
 
 class JobSql implements ISqlBase {