SELECT * FROM tb_name AS a WHERE id IN(SELECT TOP 10 id FROM tb_name WHERE a.hangye=hangye ORDER BY adddate DESC)
SELECT * FROM ( SELECT rid=ROW_NUMBER() OVER(PARTITION BY hangye ORDER BY adddate DESC), * FROM tb_name ) AS T WHERE rid<=10
--按某一字段分组取最大(小)值所在行的数据(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 */
SELECT DISTINCT b.* FROM tb_name AS a CROSS APPLY ( SELECT TOP (10) * FROM tb_name WHERE hangye=a.hangye ORDER BY addate DESC ) AS b
看1楼SELECT * FROM tb_name AS a WHERE 10>(SELECT COUNT(*) FROM tb_name WHERE hangye=a.hangye AND adddate>a.adddate)
SELECT r.ChannelnameEn,c1.NameCn,c.NameCn,N.ID,n.Title,N.CreateTime,c.FatherID,N.SecondCategoryID FROM News N left join ricclass r on r.ChannelID=n.ChannelID left join Category c on c.CategoryID=n.SecondCategoryID left join Category c1 on c1.CategoryID=c.FatherID WHERE 10>(SELECT COUNT(*) FROM News n1 left join Category c2 on c2.CategoryID=n1.SecondCategoryID WHERE c.FatherID=c2.FatherID AND CreateTime>N.CreateTime) and n.ChannelID>0 and n.SecondCategoryID>0 order by c1.NameCn,n.CreateTime DESC我已经拼好了,还能够再优化吗?
FROM tb_name AS a
WHERE id IN(SELECT TOP 10 id
FROM tb_name
WHERE a.hangye=hangye
ORDER BY adddate DESC)
FROM
(
SELECT rid=ROW_NUMBER()
OVER(PARTITION BY hangye ORDER BY adddate DESC),
*
FROM tb_name
) AS T
WHERE rid<=10
/*
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
*/
FROM tb_name AS a
CROSS APPLY
(
SELECT TOP (10) *
FROM tb_name
WHERE hangye=a.hangye
ORDER BY addate DESC
) AS b
sql2000就麻烦了,只能用count嵌套模拟,而且效率很低
看1楼SELECT *
FROM tb_name AS a
WHERE 10>(SELECT COUNT(*)
FROM tb_name
WHERE hangye=a.hangye
AND adddate>a.adddate)
left join ricclass r on r.ChannelID=n.ChannelID
left join Category c on c.CategoryID=n.SecondCategoryID
left join Category c1 on c1.CategoryID=c.FatherID
WHERE 10>(SELECT COUNT(*) FROM News n1 left join Category c2 on c2.CategoryID=n1.SecondCategoryID
WHERE c.FatherID=c2.FatherID AND CreateTime>N.CreateTime)
and n.ChannelID>0 and n.SecondCategoryID>0
order by c1.NameCn,n.CreateTime DESC我已经拼好了,还能够再优化吗?