如何查询两张表的唯一用户数

[fusoft]

两个表都有一个用户ID的字段，现在要合并查询两张表的唯一用户数，应该怎么写？

[SQL77]

SELECT 
(
SELECT COUNT(*) FROM TA T WHERE NOT EXISTS(SELECT 1 FROM TB WHERE ID=T.ID)
)
+
(
SELECT COUNT(*) FROM TB T WHERE NOT EXISTS(SELECT 1 FROM TA WHERE ID=T.ID)
)

[SQL77]

SELECT 
(
SELECT COUNT(DISTINCT ID) FROM TA T
)
+
(
SELECT COUNT(DISTINCT ID) FROM TB T 
)

?

[--小F--]

select
  id
from
(
select id from ta
union all
select id from tb
)t
group by id having count(1)=1

[黄_瓜]

(select * from ta
except
select * from tb
)
union all
(
select * from tb
except
select * from ta
)

[饮水需思源]

select distinct id from tmp
(select id from a
 union all
 select id from b) as tmp

[黄_瓜]

3、4、5楼同一秒 我的神呀！

[fusoft]

这么多方法。。我应该用哪一种？？

[fusoft]

已经验证了1，2，3，5楼的方法得到的结果都是错的

求两张表的唯一用户数，

如
表A

aaa
bbb
ccc

表B
aaa
ccc
ddd

两张表的唯一用户数应该为4人

[--小F--]

select
  count(1)
from
(
select id from ta
union all
select id from tb
)t
group by id 

[SQL77]

[Quote=引用 8 楼 fusoft 的回复:]
已经验证了1，2，3，5楼的方法得到的结果都是错的

求两张表的唯一用户数，

如
表A

aaa
bbb
ccc

表B
aaa
ccc
ddd

两张表的唯一用户数应该为4人
[/Quote]

汗,

SELECT COUNT(*) FROM (
select id from ta
union select id from tb)

[SQL77]

SELECT COUNT(*) 
FROM 
(
select id from ta
union 
select id from tb)
AS T

UNION 会自动去重

[fusoft]

我还是赶紧结贴吧。。