一个SQL查询语句

求一个SQL查询语句实现功能如下

表A中字段a 数据类型datetime  例 2009-1-15
a值可以是重复

要求统计出2009 每一个月份的不重复的a值有多少个

只能用一条SQL查询语句

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SQL code:

select a, 记录数=count(distinct(a)) from A
where year(a)='2009'
group by datepart(mm,a)

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SQL code:

select a.*
from tb a
where (select count(1) from tb where a.a = a)=1

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SQL code:

select mh=datepart(mm,a) 记录数=count(distinct(a)) from A
where year(a)='2009'
group by datepart(mm,a)

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SQL code:

declare @TB1 table(a datetime)
insert @TB1
select '2009-1-1' union all
select '2009-1-1' union all
select '2009-1-2' union all
select '2009-1-3' union all
select '2009-1-4'

select a.*
from @TB1 a
where (select count(1) from @TB1 where a.a = a)=1

/*
-----------------------
2009-01-02 00:00:00.000
2009-01-03 00:00:00.000
2009-01-04 00:00:00.000

(3 row(s) affected)

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SQL code

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Code highlighting produced