求一个sql语句

[hb9191]

表T:
字段：XH ZD1 ZD2
1 a1 a2
2 s2 s1
3 d7 d5
……
XH为序号

通过sql查询得到的结果为：
1 a1
2 a2
3 s2
4 s1
5 d7
6 d5
……
这个sql怎么写？谢谢！

[freetd]

WITH T AS (
	SELECT   1 a, 'a1' b, 'a2' c FROM dual
	UNION ALL SELECT  2,  's2',  's1' FROM dual
	UNION ALL SELECT  3, 'd7', 'd5' FROM dual
)
SELECT ROW_NUMBER() OVER (ORDER BY a,c) ID,b FROM(
	SELECT T.a,1 c,T.B FROM T
	UNION ALL 
	SELECT T.a,2 c, T.c FROM T ORDER BY 1
) x；

[freetd]

写错了，忘记了已经有个c列了，把c列改为d

WITH T AS (
	SELECT   1 a, 'a1' b, 'a2' c FROM dual
	UNION ALL SELECT  2,  's2',  's1' FROM dual
	UNION ALL SELECT  3, 'd7', 'd5' FROM dual
)
SELECT ROW_NUMBER() OVER (ORDER BY a,d) ID,b FROM(
	SELECT T.a,1 d,T.B FROM T
	UNION ALL 
	SELECT T.a,2 d, T.c FROM T ORDER BY 1
) x

[freetd]

两条语句的结果都是一样，改成d的别名为了好区分原来已存在的c列

[大明湖畔_帅锅]

with t1 as
(
     select 1 xh,'a1' zd1,'a2' zd2 from dual
     union all
     select 2 xh,'s2' zd1,'s1' zd2 from dual
     union all
     select 3 xh,'d7' zd1,'d5' zd2 from dual
)

select zd1
from 
(
  select xh,zd1
  from t1
  union all
  select xh+0.1,zd2
  from t1
)
order by xh
     
     zd1
----------------
1	a1
2	a2
3	s2
4	s1
5	d7
6	d5

[hb9191]

先谢谢了。但这种方法不可用呀，a1 a2 s2 s1 d7 d5 只是示意，你并不知道实际内容是什么？而且可能记录很多，无法一一列出。

我的笨办法：
SELECT xh * 2 - 1 AS xh1, xh AS xh2, zd1 FROM t
UNION
SELECT xh * 2 AS xh1, xh AS xh2, zd2 FROM t
ORDER BY xh1