fix sql

@@ -110,6 +110,11 @@ func(s *SqlExcutor)QueryExists()(exists bool,err error){
 		sqlCount = sqlCount +" limit 1"
 	}
 	if err=o.Raw(sqlCount).QueryRow(&total);err!=nil{
+		if err==orm.ErrNoRows{
+			exists =false
+			err = nil
+			return
+		}
 		return
 	}
 	exists = false