select * from aa a where not exists (select 1 from aa where datediff(day,d,a.d)=0 and d<a.d)
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from aa t
where not exists(select 1 from aa where t.a = a and t.b = b and t.d < d)
(爱新觉罗.毓华 2007-10-23于浙江杭州)
/*
数据如下:
name val memo
a 2 a2(a的第二个值)
a 1 a1--a的第一个值
a 3 a3:a的第三个值
b 1 b1--b的第一个值
b 3 b3:b的第三个值
b 2 b2b2b2b2
b 4 b4b4
b 5 b5b5b5b5b5
*/
--创建表并插入数据:
create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a', 2, 'a2(a的第二个值)')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('b', 1, 'b1--b的第一个值')
insert into tb values('b', 3, 'b3:b的第三个值')
insert into tb values('b', 2, 'b2b2b2b2')
insert into tb values('b', 4, 'b4b4')
insert into tb values('b', 5, 'b5b5b5b5b5')
go--一、按name分组取val最大的值所在行的数据。
--方法1:
select a.* from tb a where val = (select max(val) from tb where name = a.name) order by a.name
--方法2:
select a.* from tb a where not exists(select 1 from tb where name = a.name and val > a.val)
--方法3:
select a.* from tb a,(select name,max(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name
--方法4:
select a.* from tb a inner join (select name , max(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name
--方法5
select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name
/*
name val memo
---------- ----------- --------------------
a 3 a3:a的第三个值
b 5 b5b5b5b5b5
*/--二、按name分组取val最小的值所在行的数据。
--方法1:
select a.* from tb a where val = (select min(val) from tb where name = a.name) order by a.name
--方法2:
select a.* from tb a where not exists(select 1 from tb where name = a.name and val < a.val)
--方法3:
select a.* from tb a,(select name,min(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name
--方法4:
select a.* from tb a inner join (select name , min(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name
--方法5
select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val < a.val) order by a.name
/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 1 b1--b的第一个值
*/--三、按name分组取第一次出现的行所在的数据。
select a.* from tb a where val = (select top 1 val from tb where name = a.name) order by a.name
/*
name val memo
---------- ----------- --------------------
a 2 a2(a的第二个值)
b 1 b1--b的第一个值
*/--四、按name分组随机取一条数据。
select a.* from tb a where val = (select top 1 val from tb where name = a.name order by newid()) order by a.name
/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 5 b5b5b5b5b5
*/--五、按name分组取最小的两个(N个)val
select a.* from tb a where 2 > (select count(*) from tb where name = a.name and val < a.val ) order by a.name,a.val
select a.* from tb a where val in (select top 2 val from tb where name=a.name order by val) order by a.name,a.val
select a.* from tb a where exists (select count(*) from tb where name = a.name and val < a.val having Count(*) < 2) order by a.name
/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
a 2 a2(a的第二个值)
b 1 b1--b的第一个值
b 2 b2b2b2b2
*/--六、按name分组取最大的两个(N个)val
select a.* from tb a where 2 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name,a.val
select a.* from tb a where val in (select top 2 val from tb where name=a.name order by val desc) order by a.name,a.val
select a.* from tb a where exists (select count(*) from tb where name = a.name and val > a.val having Count(*) < 2) order by a.name
/*
name val memo
---------- ----------- --------------------
a 2 a2(a的第二个值)
a 3 a3:a的第三个值
b 4 b4b4
b 5 b5b5b5b5b5
*/
--七,如果整行数据有重复,所有的列都相同。
/*
数据如下:
name val memo
a 2 a2(a的第二个值)
a 1 a1--a的第一个值
a 1 a1--a的第一个值
a 3 a3:a的第三个值
a 3 a3:a的第三个值
b 1 b1--b的第一个值
b 3 b3:b的第三个值
b 2 b2b2b2b2
b 4 b4b4
b 5 b5b5b5b5b5
*/
--在sql server 2000中只能用一个临时表来解决,生成一个自增列,先对val取最大或最小,然后再通过自增列来取数据。
--创建表并插入数据:
create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a', 2, 'a2(a的第二个值)')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('b', 1, 'b1--b的第一个值')
insert into tb values('b', 3, 'b3:b的第三个值')
insert into tb values('b', 2, 'b2b2b2b2')
insert into tb values('b', 4, 'b4b4')
insert into tb values('b', 5, 'b5b5b5b5b5')
goselect * , px = identity(int,1,1) into tmp from tbselect m.name,m.val,m.memo from
(
select t.* from tmp t where val = (select min(val) from tmp where name = t.name)
) m where px = (select min(px) from
(
select t.* from tmp t where val = (select min(val) from tmp where name = t.name)
) n where n.name = m.name)drop table tb,tmp/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 1 b1--b的第一个值(2 行受影响)
*/
--在sql server 2005中可以使用row_number函数,不需要使用临时表。
--创建表并插入数据:
create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a', 2, 'a2(a的第二个值)')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('b', 1, 'b1--b的第一个值')
insert into tb values('b', 3, 'b3:b的第三个值')
insert into tb values('b', 2, 'b2b2b2b2')
insert into tb values('b', 4, 'b4b4')
insert into tb values('b', 5, 'b5b5b5b5b5')
goselect m.name,m.val,m.memo from
(
select * , px = row_number() over(order by name , val) from tb
) m where px = (select min(px) from
(
select * , px = row_number() over(order by name , val) from tb
) n where n.name = m.name)drop table tb/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 1 b1--b的第一个值(2 行受影响)
*/
select * from aa a
where not exists(select 1 from aa b where a.a=b.a and a.d<b.d )
if object_id('tempdb.dbo.#aa') is not null drop table #aa
create table #aa (a varchar(2),b varchar(2),c varchar(2),d datetime)
insert into #aa
select 'a1','b1','c1','2008-05-01 11:10:10' union all
select 'a1','b1','c2','2008-05-01 12:12:13' union all
select 'a2','b2','c3','2008-05-02 13:10:10' union all
select 'a2','b2','c4','2008-05-02 15:13:13' union all
select 'a3','b3','c5','2008-05-03 01:12:12' union all
select 'a3','b3','c6','2008-05-03 12:12:12'select * from #aa as t where d=(select max(d) from #aa where datediff(day,d,t.d)=0)/*
a b c d
---- ---- ---- -----------------------
a1 b1 c2 2008-05-01 12:12:13.000
a2 b2 c4 2008-05-02 15:13:13.000
a3 b3 c6 2008-05-03 12:12:12.000
*/
insert into aa values('a1' , 'b1' , 'c1' , '2008-05-01 11:10:10')
insert into aa values('a1' , 'b1' , 'c2' , '2008-05-01 12:12:13')
insert into aa values('a2' , 'b2' , 'c3' , '2008-05-02 13:10:10')
insert into aa values('a2' , 'b2' , 'c4' , '2008-05-02 15:13:13')
insert into aa values('a3' , 'b3' , 'c5' , '2008-05-03 01:12:12')
insert into aa values('a3' , 'b3' , 'c6' , '2008-05-03 12:12:12')
goselect t.* from aa t where convert(varchar(8),d,114) = (select max(convert(varchar(8),d,114)) from aa where convert(varchar(10),d,120) = convert(varchar(10),t.d,120))drop table aa/*
a b c d
---------- ---------- ---------- ------------------------------------------------------
a1 b1 c2 2008-05-01 12:12:13.000
a2 b2 c4 2008-05-02 15:13:13.000
a3 b3 c6 2008-05-03 12:12:12.000(所影响的行数为 3 行)
*/
insert into aa values('a1' , 'b1' , 'c1' , '2008-05-01 11:10:10')
insert into aa values('a1' , 'b1' , 'c2' , '2008-05-01 12:12:13')
insert into aa values('a2' , 'b2' , 'c3' , '2008-05-02 13:10:10')
insert into aa values('a2' , 'b2' , 'c4' , '2008-05-02 15:13:13')
insert into aa values('a3' , 'b3' , 'c5' , '2008-05-03 01:12:12')
insert into aa values('a3' , 'b3' , 'c6' , '2008-05-03 12:12:12')
goselect t.* from aa t where convert(varchar(8),d,114) = (select max(convert(varchar(8),d,114)) from aa where convert(varchar(10),d,120) = convert(varchar(10),t.d,120))drop table aa/*
a b c d
---------- ---------- ---------- ------------------------------------------------------
a1 b1 c2 2008-05-01 12:12:13.000
a2 b2 c4 2008-05-02 15:13:13.000
a3 b3 c6 2008-05-03 12:12:12.000(所影响的行数为 3 行)
*/