diff --git a/chain.go b/chain.go
index aa65e357..b45a373b 100644
--- a/chain.go
+++ b/chain.go
@@ -7,9 +7,9 @@ import (
 )
 
 type Chain struct {
-	db     sql_common
-	driver string
-	value  interface{}
+	d     *DB
+	db    sql_common
+	value interface{}
 
 	Errors []error
 	Error  error
@@ -27,6 +27,9 @@ type Chain struct {
 	unscoped           bool
 }
 
+func (s *Chain) driver() string {
+	return s.d.driver
+}
 func (s *Chain) err(err error) error {
 	if err != nil {
 		s.Errors = append(s.Errors, err)
@@ -49,7 +52,6 @@ func (s *Chain) do(value interface{}) (do *Do) {
 	do = &Do{
 		chain:              s,
 		db:                 s.db,
-		driver:             s.driver,
 		whereClause:        s.whereClause,
 		orClause:           s.orClause,
 		notClause:          s.notClause,
diff --git a/do.go b/do.go
index 49c4dc80..546cb7c4 100644
--- a/do.go
+++ b/do.go
@@ -15,7 +15,6 @@ import (
 type Do struct {
 	chain              *Chain
 	db                 sql_common
-	driver             string
 	guessedTableName   string
 	specifiedTableName string
 
@@ -59,14 +58,14 @@ func (s *Do) hasError() bool {
 }
 
 func (s *Do) setModel(value interface{}) *Do {
-	s.model = &Model{data: value, driver: s.driver}
+	s.model = &Model{data: value, do: s}
 	s.value = value
 	return s
 }
 
 func (s *Do) addToVars(value interface{}) string {
 	s.sqlVars = append(s.sqlVars, value)
-	if s.driver == "postgres" {
+	if s.chain.driver() == "postgres" {
 		return fmt.Sprintf("$%d", len(s.sqlVars))
 	} else {
 		return "?"
@@ -116,14 +115,14 @@ func (s *Do) prepareCreateSql() {
 func (s *Do) saveBeforeAssociations() {
 	for _, field := range s.model.beforeAssociations() {
 		var id interface{}
-		do := &Do{chain: s.chain, db: s.db, driver: s.driver}
+		do := &Do{chain: s.chain, db: s.db}
 
 		reflect_value := reflect.ValueOf(field.Value)
 		if reflect_value.CanAddr() {
 			id = do.setModel(reflect_value.Addr().Interface()).save()
 		} else {
 			dest_value := reflect.New(reflect_value.Type()).Elem()
-			m := &Model{data: field.Value, driver: s.driver}
+			m := &Model{data: field.Value, do: s}
 			for _, f := range m.columnsHasValue("other") {
 				dest_value.FieldByName(f.Name).Set(reflect.ValueOf(f.Value))
 			}
@@ -145,20 +144,20 @@ func (s *Do) saveAfterAssociations() {
 		case reflect.Slice:
 			for i := 0; i < reflect_value.Len(); i++ {
 				value := reflect_value.Index(i).Addr().Interface()
-				do := &Do{chain: s.chain, db: s.db, driver: s.driver}
+				do := &Do{chain: s.chain, db: s.db}
 				if len(field.foreignKey) > 0 {
 					s.model.setValueByColumn(field.foreignKey, s.model.primaryKeyValue(), value)
 				}
 				do.setModel(value).save()
 			}
 		default:
-			do := &Do{chain: s.chain, db: s.db, driver: s.driver}
+			do := &Do{chain: s.chain, db: s.db}
 			if reflect_value.CanAddr() {
 				s.model.setValueByColumn(field.foreignKey, s.model.primaryKeyValue(), field.Value)
 				do.setModel(field.Value).save()
 			} else {
 				dest_value := reflect.New(reflect.TypeOf(field.Value)).Elem()
-				m := &Model{data: field.Value, driver: s.driver}
+				m := &Model{data: field.Value, do: s}
 				for _, f := range m.columnsHasValue("other") {
 					dest_value.FieldByName(f.Name).Set(reflect.ValueOf(f.Value))
 				}
@@ -181,7 +180,7 @@ func (s *Do) create() (i interface{}) {
 
 	if !s.hasError() {
 		var id interface{}
-		if s.driver == "postgres" {
+		if s.chain.driver() == "postgres" {
 			s.err(s.db.QueryRow(s.sql, s.sqlVars...).Scan(&id))
 		} else {
 			if sql_result, err := s.db.Exec(s.sql, s.sqlVars...); s.err(err) == nil {
@@ -216,7 +215,7 @@ func (s *Do) setUpdateAttrs(values interface{}, ignore_protected_attrs ...bool)
 			s.setUpdateAttrs(value, ignore_protected_attrs...)
 		}
 	case interface{}:
-		m := &Model{data: values, driver: s.driver}
+		m := &Model{data: values, do: s}
 		fields := m.columnsHasValue("other")
 
 		s.updateAttrs = make(map[string]interface{}, len(fields))
@@ -348,8 +347,8 @@ func (s *Do) related(value interface{}, foreign_keys ...string) {
 	var foreign_key string
 	var err error
 
-	from := &Model{data: value, driver: s.driver}
-	to := &Model{data: s.value, driver: s.driver}
+	from := &Model{data: value, do: s}
+	to := &Model{data: s.value, do: s}
 	foreign_keys = append(foreign_keys, from.typeName()+"Id", to.typeName()+"Id")
 
 	for _, fk := range foreign_keys {
@@ -535,7 +534,7 @@ func (s *Do) buildWhereCondition(clause map[string]interface{}) (str string) {
 		}
 		return strings.Join(sqls, " AND ")
 	case interface{}:
-		m := &Model{data: query, driver: s.driver}
+		m := &Model{data: query, do: s}
 		var sqls []string
 		for _, field := range m.columnsHasValue("other") {
 			sqls = append(sqls, fmt.Sprintf(" ( %v = %v ) ", field.DbName, s.addToVars(field.Value)))
@@ -596,7 +595,7 @@ func (s *Do) buildNotCondition(clause map[string]interface{}) (str string) {
 		}
 		return strings.Join(sqls, " AND ")
 	case interface{}:
-		m := &Model{data: query, driver: s.driver}
+		m := &Model{data: query, do: s}
 		var sqls []string
 		for _, field := range m.columnsHasValue("other") {
 			sqls = append(sqls, fmt.Sprintf(" ( %v <> %v ) ", field.DbName, s.addToVars(field.Value)))
@@ -759,7 +758,7 @@ func (s *Do) autoMigrate() *Do {
 }
 
 func (s *Do) initializeWithSearchCondition() {
-	m := Model{data: s.value, driver: s.driver}
+	m := Model{data: s.value, do: s}
 
 	for _, clause := range s.whereClause {
 		query := clause["query"]
@@ -772,7 +771,7 @@ func (s *Do) initializeWithSearchCondition() {
 			for _, obj := range query.([]interface{}) {
 				switch reflect.ValueOf(obj).Kind() {
 				case reflect.Struct:
-					m := &Model{data: obj, driver: s.driver}
+					m := &Model{data: obj, do: s}
 					for _, field := range m.columnsHasValue("other") {
 						m.setValueByColumn(field.DbName, field.Value, s.value)
 					}
@@ -783,7 +782,7 @@ func (s *Do) initializeWithSearchCondition() {
 				}
 			}
 		case interface{}:
-			m := &Model{data: query, driver: s.driver}
+			m := &Model{data: query, do: s}
 			for _, field := range m.columnsHasValue("other") {
 				m.setValueByColumn(field.DbName, field.Value, s.value)
 			}
diff --git a/main.go b/main.go
index 3d7d9d02..da8d33f1 100644
--- a/main.go
+++ b/main.go
@@ -34,7 +34,7 @@ func (s *DB) SingularTable(result bool) {
 }
 
 func (s *DB) buildChain() *Chain {
-	return &Chain{db: s.db, driver: s.driver}
+	return &Chain{db: s.db, d: s}
 }
 
 func (s *DB) Where(querystring interface{}, args ...interface{}) *Chain {
diff --git a/model.go b/model.go
index 50f7743b..c63392fc 100644
--- a/model.go
+++ b/model.go
@@ -13,7 +13,7 @@ import (
 
 type Model struct {
 	data          interface{}
-	driver        string
+	do            *Do
 	_cache_fields map[string][]Field
 }
 
@@ -110,7 +110,7 @@ func (m *Model) fields(operation string) (fields []Field) {
 					if is_scanner {
 						field.IsBlank = !value.FieldByName("Valid").Interface().(bool)
 					} else {
-						m := &Model{data: value.Interface(), driver: m.driver}
+						m := &Model{data: value.Interface(), do: m.do}
 
 						fields := m.columnsHasValue("other")
 						if len(fields) == 0 {
@@ -135,9 +135,9 @@ func (m *Model) fields(operation string) (fields []Field) {
 						value.Set(reflect.ValueOf(time.Now()))
 					}
 				}
-				field.SqlType = getSqlType(m.driver, value, 0)
+				field.SqlType = getSqlType(m.do.chain.driver(), value, 0)
 			} else if field.IsPrimaryKey {
-				field.SqlType = getPrimaryKeySqlType(m.driver, value, 0)
+				field.SqlType = getPrimaryKeySqlType(m.do.chain.driver(), value, 0)
 			} else {
 				field_value := reflect.Indirect(value)
 
@@ -152,7 +152,7 @@ func (m *Model) fields(operation string) (fields []Field) {
 					_, is_scanner := reflect.New(field_value.Type()).Interface().(sql.Scanner)
 
 					if is_scanner {
-						field.SqlType = getSqlType(m.driver, value, 0)
+						field.SqlType = getSqlType(m.do.chain.driver(), value, 0)
 					} else {
 						if indirect_value.FieldByName(p.Name + "Id").IsValid() {
 							field.foreignKey = p.Name + "Id"
@@ -166,7 +166,7 @@ func (m *Model) fields(operation string) (fields []Field) {
 						}
 					}
 				default:
-					field.SqlType = getSqlType(m.driver, value, 0)
+					field.SqlType = getSqlType(m.do.chain.driver(), value, 0)
 				}
 			}
 
@@ -326,7 +326,7 @@ func (m *Model) callMethod(method string) error {
 }
 
 func (m *Model) returningStr() (str string) {
-	if m.driver == "postgres" {
+	if m.do.chain.driver() == "postgres" {
 		str = fmt.Sprintf("RETURNING \"%v\"", m.primaryKeyDb())
 	}
 	return