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declare @T table(id int, A int, B int, C int)
insert @T select 1, 1, 1, 10
insert @T select 2, 1, 2, 20
insert @T select 3, 2, 1, 100
insert @T select 4, 2, 2, 200
insert @T select 5, 3, 2, 1000
insert @T select 6, 3, 3, 2000
insert @T select 7, 3, 4, 3000
select *
from @T t
where (select count(1) from @t where a=t.a and b<t.b)=0
(所影响的行数为 1 行)
(所影响的行数为 1 行)
(所影响的行数为 1 行)
(所影响的行数为 1 行)
(所影响的行数为 1 行)
(所影响的行数为 1 行)
(所影响的行数为 1 行)
id A B C
----------- ----------- ----------- -----------
1 1 1 10
3 2 1 100
5 3 2 1000
(所影响的行数为 3 行)
create table tb(id int, A int, B int, C int)
insert into tb values(1, 1, 1, 10 )
insert into tb values(2, 1, 2, 20 )
insert into tb values(3, 2, 1, 100 )
insert into tb values(4, 2, 2, 200 )
insert into tb values(5, 3, 2, 1000 )
insert into tb values(6, 3, 3, 2000 )
insert into tb values(7, 3, 4, 3000 )
go
--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 b = (select min(b) from tb where a = a.a) order by a.a
--方法2:
select a.* from tb a where not exists(select 1 from tb where a = a.a and b < a.b) order by a.a
--方法3:
select a.* from tb a,(select a,min(b) b from tb group by a) b where a.a = b.a and a.b = b.b order by a.a
--方法4:
select a.* from tb a inner join (select a , min(b) b from tb group by a) b on a.a = b.a and a.b = b.b order by a.a
--方法5
select a.* from tb a where 1 > (select count(*) from tb where a = a.a and b < a.b) order by a.a
drop table tb
/*
id A B C
----------- ----------- ----------- -----------
1 1 1 10
3 2 1 100
5 3 2 1000
(3 行受影响)
id A B C
----------- ----------- ----------- -----------
1 1 1 10
3 2 1 100
5 3 2 1000
(3 行受影响)
id A B C
----------- ----------- ----------- -----------
1 1 1 10
3 2 1 100
5 3 2 1000
(3 行受影响)
id A B C
----------- ----------- ----------- -----------
1 1 1 10
3 2 1 100
5 3 2 1000
(3 行受影响)
id A B C
----------- ----------- ----------- -----------
1 1 1 10
3 2 1 100
5 3 2 1000
(3 行受影响)
*/
declare @T table(id int, A int, B int, C int)
insert @T select 1, 1, 1, 10
insert @T select 2, 1, 2, 20
insert @T select 3, 2, 1, 100
insert @T select 4, 2, 2, 200
insert @T select 5, 3, 2, 1000
insert @T select 6, 3, 3, 2000
insert @T select 7, 3, 4, 3000
select * from @T t where not exists(select 1 from @t where a=t.a and b<t.b)
(所影响的行数为 1 行)
id A B C
----------- ----------- ----------- -----------
1 1 1 10
3 2 1 100
5 3 2 1000
(所影响的行数为 3 行)
create table tb(id int, A int, B int, C int)
insert into tb values(1, 1, 1, 10 )
insert into tb values(2, 1, 2, 20 )
insert into tb values(3, 2, 1, 100 )
insert into tb values(4, 2, 2, 200 )
insert into tb values(5, 3, 2, 1000 )
insert into tb values(6, 3, 3, 2000 )
insert into tb values(7, 3, 4, 3000 )
go
select t.* from tb t where b = (select min(b) from tb where a = t.a) order by a
drop table tb
/*
id A B C
----------- ----------- ----------- -----------
1 1 1 10
3 2 1 100
5 3 2 1000
(3 行受影响)
*/
--按某一字段分组取最大(小)值所在行的数据
(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')
go
select * , px = identity(int,1,1) into tmp from tb
select 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')
go
select 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 t.* from tb t where b = (select min(b) from tb where a = b.a)