请教一则简单的SQL查询问题

语法如下：

mysql> select '1' as `a`, '2' as `b`, '3' as `c`;
+---+---+---+
| a | b | c |
+---+---+---+
| 1 | 2 | 3 |
+---+---+---+
1 row in set (0.00 sec)

我希望打印增加一行，怎么做，比如：

mysql> select '1' as `a`, '2' as `b`, '3' as `c`;
+---+---+---+
| a | b | c |
+---+---+---+
| 1 | 2 | 3 |
+---+---+---+
| 4 | 5 | 6 |
+---+---+---+

---

select '1' as `a`, '2' as `b`, '3' as `c`
union all
select '4' as `a`, '5' as `b`, '6' as `c`