请问一个关于合并的sql语句

[Heray]

假设有两张表A和B,分别有两个字段a,b,我现在需要用一个sql语句将这两个字段合并到一个新表的字段中(不重复),请问如何解决?
比如
A表 B表
a b
1 1
2 3
3 5
4 7

输出字段为

1
2
3
4
5
7

[WangZWang]

select c.ab
from (Select a as ab from A表
union
Select b as ab from B表) as c

[Well]

select distinct ab
from
(
select a as ab from a
union
select b as ab from b
) C

[Well]

1:
select ab
from
(
select a as ab from a
union
select b as ab from b
) C
2:
select distinct ab
from
(
select a as ab from a
union all
select b as ab from b
) C

[hsj20041004]

TO: Hopewell_Go(好的在后頭﹗希望更好﹗﹗)
这不是多此一举！！
select distinct ab
from
(
select a as ab from a
union all
select b as ab from b
) C

[hr88rong]

select distinct ab
from
(
select a as ab from a
union all
select b as ab from b
)AS C '这边要不要AS C 啊?我觉得要哦!