diff --git a/callback_create.go b/callback_create.go
index b8725363..0ba3feac 100644
--- a/callback_create.go
+++ b/callback_create.go
@@ -71,29 +71,32 @@ func createCallback(scope *Scope) {
 			}
 		}
 
-		returningKey := "*"
-		primaryField := scope.PrimaryField()
+		var (
+			returningColumn = "*"
+			quotedTableName = scope.QuotedTableName()
+			primaryField    = scope.PrimaryField()
+		)
+
 		if primaryField != nil {
-			returningKey = scope.Quote(primaryField.DBName)
+			returningColumn = scope.Quote(primaryField.DBName)
 		}
 
+		lastInsertIdReturningSuffix := scope.Dialect().LastInsertIdReturningSuffix(quotedTableName, returningColumn)
+
 		if len(columns) == 0 {
-			scope.Raw(fmt.Sprintf("INSERT INTO %v DEFAULT VALUES %v",
-				scope.QuotedTableName(),
-				scope.Dialect().ReturningStr(scope.QuotedTableName(), returningKey),
-			))
+			scope.Raw(fmt.Sprintf("INSERT INTO %v DEFAULT VALUES %v", quotedTableName, lastInsertIdReturningSuffix))
 		} else {
 			scope.Raw(fmt.Sprintf(
 				"INSERT INTO %v (%v) VALUES (%v) %v",
 				scope.QuotedTableName(),
 				strings.Join(columns, ","),
 				strings.Join(placeholders, ","),
-				scope.Dialect().ReturningStr(scope.QuotedTableName(), returningKey),
+				lastInsertIdReturningSuffix,
 			))
 		}
 
 		// execute create sql
-		if scope.Dialect().SupportLastInsertId() || primaryField == nil {
+		if lastInsertIdReturningSuffix == "" || primaryField == nil {
 			if result, err := scope.SqlDB().Exec(scope.Sql, scope.SqlVars...); scope.Err(err) == nil {
 				// set rows affected count
 				scope.db.RowsAffected, _ = result.RowsAffected()
diff --git a/dialect.go b/dialect.go
index 1fa61925..72b6b2aa 100644
--- a/dialect.go
+++ b/dialect.go
@@ -5,21 +5,30 @@ import (
 	"reflect"
 )
 
+// Dialect interface contains behaviors that differ across SQL database
 type Dialect interface {
-	BinVar(i int) string
+	// BindVar return the placeholder for actual values in SQL statements, in many dbs it is "?", Postgres using $1
+	BindVar(i int) string
+	// Quote quotes field name to avoid SQL parsing exceptions by using a reserved word as a field name
 	Quote(key string) string
-	SqlTag(value reflect.Value, size int, autoIncrease bool) string
+	// DataTypeOf return data's sql type
+	DataTypeOf(value reflect.Value, size int, autoIncrease bool) string
 
+	// HasIndex check has index or not
 	HasIndex(scope *Scope, tableName string, indexName string) bool
+	// RemoveIndex remove index
 	RemoveIndex(scope *Scope, indexName string)
+	// HasTable check has table or not
 	HasTable(scope *Scope, tableName string) bool
+	// HasColumn check has column or not
 	HasColumn(scope *Scope, tableName string, columnName string) bool
-	CurrentDatabase(scope *Scope) string
 
-	ReturningStr(tableName, key string) string
+	// LimitAndOffsetSQL return generate SQL with limit and offset, as mssql has special case
 	LimitAndOffsetSQL(limit, offset int) string
+	// SelectFromDummyTable return select values, for most dbs, `SELECT values` just works, mysql needs `SELECT value FROM DUAL`
 	SelectFromDummyTable() string
-	SupportLastInsertId() bool
+	// LastInsertIdReturningSuffix most dbs support LastInsertId, but postgres needs to use `RETURNING`
+	LastInsertIdReturningSuffix(tableName, columnName string) string
 }
 
 func NewDialect(driver string) Dialect {
diff --git a/dialect_common.go b/dialect_common.go
index ade7c068..efc8d642 100644
--- a/dialect_common.go
+++ b/dialect_common.go
@@ -8,7 +8,7 @@ import (
 
 type commonDialect struct{}
 
-func (commonDialect) BinVar(i int) string {
+func (commonDialect) BindVar(i int) string {
 	return "$$" // ?
 }
 
@@ -16,7 +16,7 @@ func (commonDialect) Quote(key string) string {
 	return fmt.Sprintf(`"%s"`, key)
 }
 
-func (commonDialect) SqlTag(value reflect.Value, size int, autoIncrease bool) string {
+func (commonDialect) DataTypeOf(value reflect.Value, size int, autoIncrease bool) string {
 	switch value.Kind() {
 	case reflect.Bool:
 		return "BOOLEAN"
@@ -55,7 +55,7 @@ func (commonDialect) SqlTag(value reflect.Value, size int, autoIncrease bool) st
 func (c commonDialect) HasIndex(scope *Scope, tableName string, indexName string) bool {
 	var (
 		count        int
-		databaseName = c.CurrentDatabase(scope)
+		databaseName = c.currentDatabase(scope)
 	)
 	c.RawScanInt(scope, &count, "SELECT count(*) FROM INFORMATION_SCHEMA.STATISTICS WHERE table_schema = ? AND table_name = ? AND index_name = ?", databaseName, tableName, indexName)
 	return count > 0
@@ -68,7 +68,7 @@ func (commonDialect) RemoveIndex(scope *Scope, indexName string) {
 func (c commonDialect) HasTable(scope *Scope, tableName string) bool {
 	var (
 		count        int
-		databaseName = c.CurrentDatabase(scope)
+		databaseName = c.currentDatabase(scope)
 	)
 	c.RawScanInt(scope, &count, "SELECT count(*) FROM INFORMATION_SCHEMA.TABLES WHERE table_schema = ? AND table_name = ?", databaseName, tableName)
 	return count > 0
@@ -77,7 +77,7 @@ func (c commonDialect) HasTable(scope *Scope, tableName string) bool {
 func (c commonDialect) HasColumn(scope *Scope, tableName string, columnName string) bool {
 	var (
 		count        int
-		databaseName = c.CurrentDatabase(scope)
+		databaseName = c.currentDatabase(scope)
 	)
 	c.RawScanInt(scope, &count, "SELECT count(*) FROM INFORMATION_SCHEMA.COLUMNS WHERE table_schema = ? AND table_name = ? AND column_name = ?", databaseName, tableName, columnName)
 	return count > 0
@@ -95,15 +95,11 @@ func (commonDialect) RawScanString(scope *Scope, scanPtr *string, query string,
 	scope.Err(scope.NewDB().Raw(query, args...).Row().Scan(scanPtr))
 }
 
-func (commonDialect) CurrentDatabase(scope *Scope) (name string) {
+func (commonDialect) currentDatabase(scope *Scope) (name string) {
 	scope.Err(scope.NewDB().Raw("SELECT DATABASE()").Row().Scan(&name))
 	return
 }
 
-func (commonDialect) ReturningStr(tableName, key string) string {
-	return ""
-}
-
 func (commonDialect) LimitAndOffsetSQL(limit, offset int) (sql string) {
 	if limit >= 0 {
 		sql += fmt.Sprintf(" LIMIT %d", limit)
@@ -118,6 +114,6 @@ func (commonDialect) SelectFromDummyTable() string {
 	return ""
 }
 
-func (commonDialect) SupportLastInsertId() bool {
-	return true
+func (commonDialect) LastInsertIdReturningSuffix(tableName, columnName string) string {
+	return ""
 }
diff --git a/dialect_mssql.go b/dialect_mssql.go
index 82fba7d1..c3e21c97 100644
--- a/dialect_mssql.go
+++ b/dialect_mssql.go
@@ -10,7 +10,7 @@ type mssql struct {
 	commonDialect
 }
 
-func (mssql) SqlTag(value reflect.Value, size int, autoIncrease bool) string {
+func (mssql) DataTypeOf(value reflect.Value, size int, autoIncrease bool) string {
 	switch value.Kind() {
 	case reflect.Bool:
 		return "bit"
@@ -55,7 +55,7 @@ func (s mssql) HasIndex(scope *Scope, tableName string, indexName string) bool {
 func (s mssql) HasTable(scope *Scope, tableName string) bool {
 	var (
 		count        int
-		databaseName = s.CurrentDatabase(scope)
+		databaseName = s.currentDatabase(scope)
 	)
 	s.RawScanInt(scope, &count, "SELECT count(*) FROM INFORMATION_SCHEMA.tables WHERE table_name = ? AND table_catalog = ?", tableName, databaseName)
 	return count > 0
@@ -64,13 +64,13 @@ func (s mssql) HasTable(scope *Scope, tableName string) bool {
 func (s mssql) HasColumn(scope *Scope, tableName string, columnName string) bool {
 	var (
 		count        int
-		databaseName = s.CurrentDatabase(scope)
+		databaseName = s.currentDatabase(scope)
 	)
 	s.RawScanInt(scope, &count, "SELECT count(*) FROM information_schema.columns WHERE table_catalog = ? AND table_name = ? AND column_name = ?", databaseName, tableName, columnName)
 	return count > 0
 }
 
-func (s mssql) CurrentDatabase(scope *Scope) (name string) {
+func (s mssql) currentDatabase(scope *Scope) (name string) {
 	s.RawScanString(scope, &name, "SELECT DB_NAME() AS [Current Database]")
 	return
 }
diff --git a/dialect_mysql.go b/dialect_mysql.go
index b6f9a22b..e334c7a4 100644
--- a/dialect_mysql.go
+++ b/dialect_mysql.go
@@ -14,7 +14,7 @@ func (mysql) Quote(key string) string {
 	return fmt.Sprintf("`%s`", key)
 }
 
-func (mysql) SqlTag(value reflect.Value, size int, autoIncrease bool) string {
+func (mysql) DataTypeOf(value reflect.Value, size int, autoIncrease bool) string {
 	switch value.Kind() {
 	case reflect.Bool:
 		return "boolean"
@@ -60,7 +60,7 @@ func (mysql) SqlTag(value reflect.Value, size int, autoIncrease bool) string {
 	panic(fmt.Sprintf("invalid sql type %s (%s) for mysql", value.Type().Name(), value.Kind().String()))
 }
 
-func (s mysql) CurrentDatabase(scope *Scope) (name string) {
+func (s mysql) currentDatabase(scope *Scope) (name string) {
 	s.RawScanString(scope, &name, "SELECT DATABASE()")
 	return
 }
diff --git a/dialect_postgres.go b/dialect_postgres.go
index 0b16816c..c4742aec 100644
--- a/dialect_postgres.go
+++ b/dialect_postgres.go
@@ -15,11 +15,11 @@ type postgres struct {
 	commonDialect
 }
 
-func (postgres) BinVar(i int) string {
+func (postgres) BindVar(i int) string {
 	return fmt.Sprintf("$%v", i)
 }
 
-func (postgres) SqlTag(value reflect.Value, size int, autoIncrease bool) string {
+func (postgres) DataTypeOf(value reflect.Value, size int, autoIncrease bool) string {
 	switch value.Kind() {
 	case reflect.Bool:
 		return "boolean"
@@ -80,12 +80,12 @@ func (s postgres) HasColumn(scope *Scope, tableName string, columnName string) b
 	return count > 0
 }
 
-func (s postgres) CurrentDatabase(scope *Scope) (name string) {
+func (s postgres) currentDatabase(scope *Scope) (name string) {
 	s.RawScanString(scope, &name, "SELECT CURRENT_DATABASE()")
 	return
 }
 
-func (s postgres) ReturningStr(tableName, key string) string {
+func (s postgres) LastInsertIdReturningSuffix(tableName, key string) string {
 	return fmt.Sprintf("RETURNING %v.%v", tableName, key)
 }
 
diff --git a/dialect_sqlite3.go b/dialect_sqlite3.go
index 82546dbb..e1e35bf7 100644
--- a/dialect_sqlite3.go
+++ b/dialect_sqlite3.go
@@ -10,7 +10,7 @@ type sqlite3 struct {
 	commonDialect
 }
 
-func (sqlite3) SqlTag(value reflect.Value, size int, autoIncrease bool) string {
+func (sqlite3) DataTypeOf(value reflect.Value, size int, autoIncrease bool) string {
 	switch value.Kind() {
 	case reflect.Bool:
 		return "bool"
@@ -65,7 +65,7 @@ func (s sqlite3) HasColumn(scope *Scope, tableName string, columnName string) bo
 	return count > 0
 }
 
-func (sqlite3) CurrentDatabase(scope *Scope) (name string) {
+func (sqlite3) currentDatabase(scope *Scope) (name string) {
 	var (
 		ifaces   = make([]interface{}, 3)
 		pointers = make([]*string, 3)
diff --git a/main.go b/main.go
index 461329fa..10c1b9be 100644
--- a/main.go
+++ b/main.go
@@ -453,14 +453,6 @@ func (s *DB) RemoveIndex(indexName string) *DB {
 	return scope.db
 }
 
-func (s *DB) CurrentDatabase() string {
-	var (
-		scope = s.clone().NewScope(s.Value)
-		name  = s.dialect.CurrentDatabase(scope)
-	)
-	return name
-}
-
 // AddForeignKey Add foreign key to the given scope
 // Example: db.Model(&User{}).AddForeignKey("city_id", "cities(id)", "RESTRICT", "RESTRICT")
 func (s *DB) AddForeignKey(field string, dest string, onDelete string, onUpdate string) *DB {
diff --git a/model_struct.go b/model_struct.go
index b47f8534..c81dcd88 100644
--- a/model_struct.go
+++ b/model_struct.go
@@ -555,7 +555,7 @@ func (scope *Scope) generateSqlTag(field *StructField) string {
 			autoIncrease = false
 		}
 
-		sqlType = scope.Dialect().SqlTag(reflectValue, size, autoIncrease)
+		sqlType = scope.Dialect().DataTypeOf(reflectValue, size, autoIncrease)
 	}
 
 	if strings.TrimSpace(additionalType) == "" {
diff --git a/query_test.go b/query_test.go
index a7d5bc0e..b762dee5 100644
--- a/query_test.go
+++ b/query_test.go
@@ -621,14 +621,3 @@ func TestSelectWithArrayInput(t *testing.T) {
 		t.Errorf("Should have selected both age and name")
 	}
 }
-
-func TestCurrentDatabase(t *testing.T) {
-	databaseName := DB.CurrentDatabase()
-	if err := DB.Error; err != nil {
-		t.Errorf("Problem getting current db name: %s", err)
-	}
-	if databaseName == "" {
-		t.Errorf("Current db name returned empty; this should never happen!")
-	}
-	t.Logf("Got current db name: %v", databaseName)
-}
diff --git a/scope.go b/scope.go
index 8ee4bdd5..6d9303ec 100644
--- a/scope.go
+++ b/scope.go
@@ -229,7 +229,7 @@ func (scope *Scope) AddToVars(value interface{}) string {
 	}
 
 	scope.SqlVars = append(scope.SqlVars, value)
-	return scope.Dialect().BinVar(len(scope.SqlVars))
+	return scope.Dialect().BindVar(len(scope.SqlVars))
 }
 
 type tabler interface {
diff --git a/scope_private.go b/scope_private.go
index dc1676e8..d5d384af 100644
--- a/scope_private.go
+++ b/scope_private.go
@@ -518,7 +518,7 @@ func (scope *Scope) createJoinTable(field *StructField) {
 					value := reflect.Indirect(reflect.New(field.Struct.Type))
 					primaryKeySqlType := field.TagSettings["TYPE"]
 					if primaryKeySqlType == "" {
-						primaryKeySqlType = scope.Dialect().SqlTag(value, 255, false)
+						primaryKeySqlType = scope.Dialect().DataTypeOf(value, 255, false)
 					}
 					sqlTypes = append(sqlTypes, scope.Quote(relationship.ForeignDBNames[idx])+" "+primaryKeySqlType)
 					primaryKeys = append(primaryKeys, scope.Quote(relationship.ForeignDBNames[idx]))
@@ -530,7 +530,7 @@ func (scope *Scope) createJoinTable(field *StructField) {
 					value := reflect.Indirect(reflect.New(field.Struct.Type))
 					primaryKeySqlType := field.TagSettings["TYPE"]
 					if primaryKeySqlType == "" {
-						primaryKeySqlType = scope.Dialect().SqlTag(value, 255, false)
+						primaryKeySqlType = scope.Dialect().DataTypeOf(value, 255, false)
 					}
 					sqlTypes = append(sqlTypes, scope.Quote(relationship.AssociationForeignDBNames[idx])+" "+primaryKeySqlType)
 					primaryKeys = append(primaryKeys, scope.Quote(relationship.AssociationForeignDBNames[idx]))