/*
數(shù)據(jù)如下：
name val memo
a 2 a2(a的第二個(gè)值)
a 1 a1--a的第一個(gè)值
a 3 a3:a的第三個(gè)值
b 1 b1--b的第一個(gè)值
b 3 b3:b的第三個(gè)值
b 2 b2b2b2b2
b 4 b4b4
b 5 b5b5b5b5b5
*/
--創(chuàng)建表并插入數(shù)據(jù)：
create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a', 2, 'a2(a的第二個(gè)值)')
insert into tb values('a', 1, 'a1--a的第一個(gè)值')
insert into tb values('a', 3, 'a3:a的第三個(gè)值')
insert into tb values('b', 1, 'b1--b的第一個(gè)值')
insert into tb values('b', 3, 'b3:b的第三個(gè)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分組取val最大的值所在行的數(shù)據(jù)。
--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的第三個(gè)值
b 5 b5b5b5b5b5
*/
--二、按name分組取val最小的值所在行的數(shù)據(jù)。
--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的第一個(gè)值
b 1 b1--b的第一個(gè)值
*/
--三、按name分組取第一次出現(xiàn)的行所在的數(shù)據(jù)。
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的第二個(gè)值)
b 1 b1--b的第一個(gè)值
*/
--四、按name分組隨機(jī)取一條數(shù)據(jù)。
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的第一個(gè)值
b 5 b5b5b5b5b5
*/
--五、按name分組取最小的兩個(gè)(N個(gè))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的第一個(gè)值
a 2 a2(a的第二個(gè)值)
b 1 b1--b的第一個(gè)值
b 2 b2b2b2b2
*/
--六、按name分組取最大的兩個(gè)(N個(gè))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的第二個(gè)值)
a 3 a3:a的第三個(gè)值
b 4 b4b4
b 5 b5b5b5b5b5
*/
--七，如果整行數(shù)據(jù)有重復(fù)，所有的列都相同。
/*
數(shù)據(jù)如下：
name val memo
a 2 a2(a的第二個(gè)值)
a 1 a1--a的第一個(gè)值
a 1 a1--a的第一個(gè)值
a 3 a3:a的第三個(gè)值
a 3 a3:a的第三個(gè)值
b 1 b1--b的第一個(gè)值
b 3 b3:b的第三個(gè)值
b 2 b2b2b2b2
b 4 b4b4
b 5 b5b5b5b5b5
*/
--在sql server 2000中只能用一個(gè)臨時(shí)表來解決，生成一個(gè)自增列，先對(duì)val取最大或最小，然后再通過自增列來取數(shù)據(jù)。
--創(chuàng)建表并插入數(shù)據(jù)：
create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a', 2, 'a2(a的第二個(gè)值)')
insert into tb values('a', 1, 'a1--a的第一個(gè)值')
insert into tb values('a', 1, 'a1--a的第一個(gè)值')
insert into tb values('a', 3, 'a3:a的第三個(gè)值')
insert into tb values('a', 3, 'a3:a的第三個(gè)值')
insert into tb values('b', 1, 'b1--b的第一個(gè)值')
insert into tb values('b', 3, 'b3:b的第三個(gè)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的第一個(gè)值
b 1 b1--b的第一個(gè)值
(2 行受影響)
*/
--在sql server 2005中可以使用row_number函數(shù)，不需要使用臨時(shí)表。
--創(chuàng)建表并插入數(shù)據(jù)：
create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a', 2, 'a2(a的第二個(gè)值)')
insert into tb values('a', 1, 'a1--a的第一個(gè)值')
insert into tb values('a', 1, 'a1--a的第一個(gè)值')
insert into tb values('a', 3, 'a3:a的第三個(gè)值')
insert into tb values('a', 3, 'a3:a的第三個(gè)值')
insert into tb values('b', 1, 'b1--b的第一個(gè)值')
insert into tb values('b', 3, 'b3:b的第三個(gè)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的第一個(gè)值
b 1 b1--b的第一個(gè)值
(2 行受影響)
*/