diff --git a/src/mysql.cpp b/src/mysql.cpp
index 977651a..bc31075 100644
--- a/src/mysql.cpp
+++ b/src/mysql.cpp
@@ -719,6 +719,7 @@ module::mysql_conn::~mysql_conn()
 
 int module::mysql_conn::connect(const std::string& ipaddress, const std::string& username, const std::string& password, const std::string& database, const std::string& charset, ushort port)
 {
+    if (m_conn == nullptr) {throw std::string("Connection is nullptr");}
     ylib::mysql::mysql_conn_info info;
     info.ipaddress = ipaddress;
     info.username = username;
@@ -731,60 +732,72 @@ int module::mysql_conn::connect(const std::string& ipaddress, const std::string&
 
 void module::mysql_conn::clear()
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     m_conn->clear();
 }
 
 std::shared_ptr<module::mysql_prepare_statement> module::mysql_conn::setsql(const std::string& sql)
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     return std::make_shared<module::mysql_prepare_statement>(m_conn->setsql(sql));
 }
 
 uint64 module::mysql_conn::insert_id()
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     return m_conn->insert_id();
 }
 
 void module::mysql_conn::begin(bool autocommit)
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     m_conn->begin(autocommit);
 }
 
 void module::mysql_conn::commit()
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     m_conn->commit();
 }
 
 void module::mysql_conn::rollback()
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     m_conn->rollback();
 }
 
 void module::mysql_conn::setDatabase(const std::string& name)
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     m_conn->setDatabase(name);
 }
 
 std::string module::mysql_conn::last_error()
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     return m_conn->last_error();
 }
 std::shared_ptr<module::select> module::mysql_conn::select()
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     return std::make_shared<module::select>(m_conn, false);
 }
 
 std::shared_ptr<module::insert> module::mysql_conn::insert()
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     return std::make_shared<module::insert>(m_conn, false);
 }
 
 std::shared_ptr<module::update> module::mysql_conn::update()
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     return std::make_shared<module::update>(m_conn, false);
 }
 
 std::shared_ptr<module::delete_> module::mysql_conn::delete_()
 {
+    if (m_conn == nullptr) { throw std::string("Connection is nullptr"); }
     return std::make_shared<module::delete_>(m_conn, false);
 }
 
@@ -817,7 +830,8 @@ void module::mysql_conn::regist(sol::state* lua)
         "select", &module::mysql_conn::select,
         "update", &module::mysql_conn::update,
         "insert", &module::mysql_conn::insert,
-        "delete", &module::mysql_conn::delete_
+        "delete", &module::mysql_conn::delete_,
+        "close", &module::mysql_conn::free,
     );
 }