dialect/sql: append UNION before ORDER BY (#1761)

* fix: builder to append UNION before ORDER_BY

* gofmt builder_test.go

dialect/sql/builder.go

@@ -2320,6 +2320,9 @@ func (s *Selector) Query() (string, []interface{}) {
 		b.WriteString(" HAVING ")
 		b.Join(s.having)
 	}
+	if len(s.union) > 0 {
+		s.joinUnion(&b)
+	}
 	if len(s.order) > 0 {
 		s.joinOrder(&b)
 	}
@@ -2331,9 +2334,6 @@ func (s *Selector) Query() (string, []interface{}) {
 		b.WriteString(" OFFSET ")
 		b.WriteString(strconv.Itoa(*s.offset))
 	}
-	if len(s.union) > 0 {
-		s.joinUnion(&b)
-	}
 	s.joinLock(&b)
 	s.total = b.total
 	s.AddError(b.Err())

dialect/sql/builder_test.go

@@ -1703,3 +1703,15 @@ func TestSelectWithLock(t *testing.T) {
 	require.Equal(t, "SELECT * FROM `users` WHERE `id` = ? LOCK IN SHARE MODE", query)
 	require.Equal(t, 20, args[0])
 }
+
+func TestSelector_UnionOrderBy(t *testing.T) {
+	table := Table("users")
+	query, _ := Dialect(dialect.Postgres).
+		Select("*").
+		From(table).
+		Where(EQ("active", true)).
+		Union(Select("*").From(Table("old_users1"))).
+		OrderBy(table.C("whatever")).
+		Query()
+	require.Equal(t, `SELECT * FROM "users" WHERE "active" = $1 UNION SELECT * FROM "old_users1" ORDER BY "users"."whatever"`, query)
+}