SQL怎么去掉查询结果的重复数据

select a,max(b) as mb from ta order by max(b)
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SQL code
select a,max(b) as mb from ta order by max(b)

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select distinct a  from ta order by b desc


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这个问题看似简单，其实挺复杂的，我也没想出来。还是等下面高手来解答的吧。
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select top 10 a
from ta t
where not exists(select 1 from ta where a = t.a and b > t.b)
order by b desc
这样可以 但是查询时间过长，可以优化吗？谢谢大家

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探讨

select top 10 a
from ta t
where not exists(select 1 from ta where a = t.a and b > t.b)
order by b desc
这样可以 但是查询时间过长，可以优化吗？谢谢大家

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SQL code
declare @tb table (a nvarchar(12),b int)insert @tb  select '我',1 union allselect '我',2 union allselect '你',3 union allselect '他',4 union allselect '她',5 union allselect '她',6select a from (select  top (100) ROW_NUMBER() over(PARTITION by a order by a desc)rn ,a,b  from @tb group by a,b order by b desc) aawhere rn=1/*a她他你我*/
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select a from ta group by a order by max(b) desc
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CREATE TABLE tmp AS SELECT MIN(b) as id FROM ta GROUP BY a;
DELETE FROM ta WHERE id NOT IN (SELECT id FROM tmp )
DROP TABLE tmp

然后 select * from ta order by b desc
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select a,max(b)  
from ta
group by a
order by b desc

酱紫不可以吗？
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distinct
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SQL code
CREATE TABLE TEST2(    Name VARCHAR(10),    Id INT)GOINSERT INTO TEST2SELECT '我',1 UNIONSELECT '我',2 UNIONSELECT '你',3 UNIONSELECT '他',4 UNIONSELECT '她',5 UNIONSELECT '她',6SELECT NAMEFROM TEST2GROUP BY NameORDER BY MAX(ID) DESC
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distinct
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select top 10 a from( select distinct a,max(b) as b from ta group by b) table_A order by b desc  

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select top 10 a from ta order by b desc.
目的是取出依照b排序的a数据 其中b是不会重复的查询出的a是重复的，如何去掉！
例如 以下数据
a       b
我      1
我      2
你      3
他      4
她      5
她      6
需要得到的数据是
她
他
你
我
这样的顺序！

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之前在英文系统里，写错了。。
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