diff --git a/builder.go b/builder.go
index 9b0816d..5d57200 100644
--- a/builder.go
+++ b/builder.go
@@ -434,29 +434,31 @@ func (b *Builder) SelectRaw(expression string, bindings ...[]interface{}) *Build
 
 // CreateSub Creates a subquery and parse it.
 func (b *Builder) CreateSub(query interface{}) (string, []interface{}) {
-	var builder *Builder
-	if bT, ok := query.(*Builder); ok {
-		builder = bT
-	} else if function, ok := query.(func(builder *Builder)); ok {
-		builder = CloneBuilderWithTable(b)
-		function(builder)
-	} else if str, ok := query.(string); ok {
-		return b.ParseSub(str)
-	} else {
-		panic("can not create sub")
+	switch v := query.(type) {
+	case func(builder *Builder):
+		builder := CloneBuilderWithTable(b)
+		v(builder)
+		return b.ParseSub(builder)
+	case string, Expression, *Builder:
+		return b.ParseSub(v)
 	}
-	return b.ParseSub(builder)
+
+	panic("can not create sub")
 }
 
 /*
 ParseSub Parse the subquery into SQL and bindings.
 */
 func (b *Builder) ParseSub(query interface{}) (string, []interface{}) {
-	if s, ok := query.(string); ok {
-		return s, []interface{}{}
-	} else if builder, ok := query.(*Builder); ok {
-		return builder.ToSql(), builder.GetBindings()
+	switch v := query.(type) {
+	case string:
+		return v, []interface{}{}
+	case Expression:
+		return string(v), []interface{}{}
+	case *Builder:
+		return v.ToSql(), v.GetBindings()
 	}
+
 	panic("A subquery must be a query builder instance, a Closure, or a string.")
 }