diff --git a/database/gdb/gdb_model_select.go b/database/gdb/gdb_model_select.go
index c6c3c486d..2fea75fe5 100644
--- a/database/gdb/gdb_model_select.go
+++ b/database/gdb/gdb_model_select.go
@@ -158,7 +158,7 @@ func (m *Model) Array(fieldsAndWhere ...interface{}) ([]Value, error) {
 // see Model.Where.
 //
 // Note that it returns sql.ErrNoRows if there's no record retrieved with the given conditions
-// from table.
+// from table and <pointer> is not nil.
 //
 // Eg:
 // user := new(User)
@@ -182,14 +182,14 @@ func (m *Model) Struct(pointer interface{}, where ...interface{}) error {
 // see Model.Where.
 //
 // Note that it returns sql.ErrNoRows if there's no record retrieved with the given conditions
-// from table.
+// from table and <pointer> is not empty.
 //
 // Eg:
 // users := ([]User)(nil)
-// err := db.Table("user").Structs(&users)
+// err   := db.Table("user").Structs(&users)
 //
 // users := ([]*User)(nil)
-// err := db.Table("user").Structs(&users)
+// err   := db.Table("user").Structs(&users)
 func (m *Model) Structs(pointer interface{}, where ...interface{}) error {
 	all, err := m.All(where...)
 	if err != nil {
@@ -216,10 +216,10 @@ func (m *Model) Structs(pointer interface{}, where ...interface{}) error {
 // err  := db.Table("user").Where("id", 1).Struct(&user)
 //
 // users := ([]User)(nil)
-// err := db.Table("user").Structs(&users)
+// err   := db.Table("user").Structs(&users)
 //
 // users := ([]*User)(nil)
-// err := db.Table("user").Structs(&users)
+// err   := db.Table("user").Structs(&users)
 func (m *Model) Scan(pointer interface{}, where ...interface{}) error {
 	t := reflect.TypeOf(pointer)
 	k := t.Kind()
diff --git a/database/gdb/gdb_z_mysql_join_test.go b/database/gdb/gdb_z_mysql_join_test.go
new file mode 100644
index 000000000..da70728e0
--- /dev/null
+++ b/database/gdb/gdb_z_mysql_join_test.go
@@ -0,0 +1,59 @@
+// Copyright 2019 gf Author(https://github.com/gogf/gf). All Rights Reserved.
+//
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file,
+// You can obtain one at https://github.com/gogf/gf.
+
+package gdb_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/gogf/gf/os/gtime"
+	"github.com/gogf/gf/test/gtest"
+)
+
+func Test_Table_Join(t *testing.T) {
+	var (
+		tableUser       = "user_" + gtime.TimestampMicroStr()
+		tableUserDetail = "user_detail_" + gtime.TimestampMicroStr()
+	)
+	if _, err := db.Exec(fmt.Sprintf(`
+CREATE TABLE %s (
+  uid int(10) unsigned NOT NULL AUTO_INCREMENT,
+  name varchar(45) NOT NULL COMMENT,
+  PRIMARY KEY (uid)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+    `, tableUser)); err != nil {
+		gtest.Error(err)
+	}
+	defer dropTable(tableUser)
+
+	if _, err := db.Exec(fmt.Sprintf(`
+CREATE TABLE %s (
+  uid int(10) unsigned NOT NULL AUTO_INCREMENT,
+  name varchar(45) NOT NULL COMMENT,
+  PRIMARY KEY (uid)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+    `, tableUserDetail)); err != nil {
+		gtest.Error(err)
+	}
+	defer dropTable(tableUserDetail)
+
+	gtest.C(t, func(t *gtest.T) {
+		type EntityUser struct {
+			Uid  int
+			Name string
+		}
+		type EntityUserDetail struct {
+			Uid      int
+			TrueName string
+		}
+		type Entity struct {
+			User       *EntityUser
+			UserDetail *EntityUserDetail
+		}
+
+	})
+}
diff --git a/util/gutil/gutil_map.go b/util/gutil/gutil_map.go
index bc014dc1b..45149ea5d 100644
--- a/util/gutil/gutil_map.go
+++ b/util/gutil/gutil_map.go
@@ -26,13 +26,13 @@ func MapContains(data map[string]interface{}, key string) (ok bool) {
 	return
 }
 
-// MapDelete deletes all <key> from map <data>.
-func MapDelete(data map[string]interface{}, key ...string) {
+// MapDelete deletes all <keys> from map <data>.
+func MapDelete(data map[string]interface{}, keys ...string) {
 	if data == nil {
 		return
 	}
-	for _, v := range key {
-		delete(data, v)
+	for _, key := range keys {
+		delete(data, key)
 	}
 }
 
@@ -78,6 +78,8 @@ func MapPossibleItemByKey(data map[string]interface{}, key string) (foundKey str
 
 // MapContainsPossibleKey checks if the given <key> is contained in given map <data>.
 // It checks the key with or without cases or chars '-'/'_'/'.'/' '.
+//
+// Note that this function might be of low performance.
 func MapContainsPossibleKey(data map[string]interface{}, key string) bool {
 	if k, _ := MapPossibleItemByKey(data, key); k != "" {
 		return true