diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 6048a1c..fe760f3 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -19,7 +19,7 @@ Yii Framework 2 Change Log
 - Bug #17881: `yii\db\Query::queryScalar()` wasn’t reverting the `select`, `orderBy`, `limit`, and `offset` params if an exception occurred (brandonkelly)
 - Bug #17875: Use `move_uploaded_file()` function instead of `copy()` and `unlink()` for saving uploaded files in case of POST request (sup-ham)
 - Bug #17884: Fix 0 values in console Table rendered as empty string (mikehaertl)
-
+- Bug #13749: Fix Yii opens db connection even when hits query cache (shushenghong)
 
 2.0.32 January 21, 2020
 -----------------------
diff --git a/framework/db/Command.php b/framework/db/Command.php
index 6735607..5f487ab 100644
--- a/framework/db/Command.php
+++ b/framework/db/Command.php
@@ -1140,8 +1140,7 @@ class Command extends Component
             if (is_array($info)) {
                 /* @var $cache \yii\caching\CacheInterface */
                 $cache = $info[0];
-                $rawSql = $rawSql ?: $this->getRawSql();
-                $cacheKey = $this->getCacheKey($method, $fetchMode, $rawSql);
+                $cacheKey = $this->getCacheKey($method, $fetchMode);
                 $result = $cache->get($cacheKey);
                 if (is_array($result) && isset($result[0])) {
                     Yii::debug('Query result served from cache', 'yii\db\Command::query');
@@ -1191,15 +1190,17 @@ class Command extends Component
      * @return array the cache key
      * @since 2.0.16
      */
-    protected function getCacheKey($method, $fetchMode, $rawSql)
+    protected function getCacheKey($method, $fetchMode)
     {
+        ksort($this->params);
         return [
             __CLASS__,
             $method,
             $fetchMode,
             $this->db->dsn,
             $this->db->username,
-            $rawSql,
+            $this->getSql(),
+            json_encode($this->params),
         ];
     }
 
diff --git a/framework/db/mysql/QueryBuilder.php b/framework/db/mysql/QueryBuilder.php
index 14d729b..b938fbb 100644
--- a/framework/db/mysql/QueryBuilder.php
+++ b/framework/db/mysql/QueryBuilder.php
@@ -390,7 +390,15 @@ class QueryBuilder extends \yii\db\QueryBuilder
      */
     private function supportsFractionalSeconds()
     {
-        $version = $this->db->getSlavePdo()->getAttribute(\PDO::ATTR_SERVER_VERSION);
+        // use cache to prevent open mysql connection
+        // https://github.com/yiisoft/yii2/issues/13749#issuecomment-481657224
+        $key = [__METHOD__, $this->db->dsn];
+        $version = \Yii::$app->cache ? \Yii::$app->cache->get($key) : null;
+        if( !$version ) {
+            $version = $this->db->getSlavePdo()->getAttribute(\PDO::ATTR_SERVER_VERSION);
+            \Yii::$app->cache ? \Yii::$app->cache->set($key, $version) : null;
+        }
+        
         return version_compare($version, '5.6.4', '>=');
     }