diff --git a/library/think/Db.php b/library/think/Db.php
index a75764b7..06ba04c7 100644
--- a/library/think/Db.php
+++ b/library/think/Db.php
@@ -39,12 +39,6 @@ use think\db\Query;
  */
 class Db
 {
-    // 数组数据集
-    const RESULTSET_ARRAY = 1;
-    // 对象数据集
-    const RESULTSET_COLLECTION = 2;
-    // 自定义对象数据集
-    const RESULTSET_CLASS = 3;
     //  数据库连接实例
     private static $instance = [];
     // 查询次数
diff --git a/library/think/db/Connection.php b/library/think/db/Connection.php
index ab18a719..f927acd0 100644
--- a/library/think/db/Connection.php
+++ b/library/think/db/Connection.php
@@ -50,7 +50,7 @@ abstract class Connection
     protected $linkWrite;
 
     // 查询结果类型
-    protected $resultSetType = Db::RESULTSET_ARRAY;
+    protected $resultSetType = 'array';
     // 查询结果类型
     protected $fetchType = PDO::FETCH_ASSOC;
     // 字段属性大小写
@@ -485,13 +485,11 @@ abstract class Connection
             return new $class($result);
         }
         switch ($this->resultSetType) {
-            case Db::RESULTSET_COLLECTION:
+            case 'collection':
                 // 返回数据集Collection对象
                 $result = new Collection($result);
                 break;
-            case Db::RESULTSET_CLASS:
-                break;
-            case Db::RESULTSET_ARRAY:
+            case 'array':
             default:
                 // 返回二维数组
         }