TbDetail表:strDetectorId和strAddress是主键,分别表示仪器的编号和厂家编号。strGuid的值是唯一的,没有完全贴出来。
strGuid strDetectorId fltTemperature dtSysTime strAddress
887c80e ... 1 30 2009-8-11 17:04:35 0001
887c80e ... 1 27.5 2009-8-12 13:30:00 0001
887c80e ... 1 27.9 2009-8-13 17:48:56 0001
887c80e ... 1 27.3 2009-8-14 14:33:06 0001
887c80e ... 2 28.1 2009-8-15 9:25:19 0001
887c80e ... 2 28.1 2009-8-15 9:27:15 0001
887c80e ... 2 28 2009-8-17 14:32:41 0001
要把“每种仪器”的“最大时间”和“最大时间对应的温度”查询出来,请问怎么解决? 以下是我的SQL语句,但是有的时候查出来的数据不对。请高手帮我分析下? SELECT *
FROM (SELECT ROW_NUMBER() OVER(ORDER BY TbDetail.strDetectorId) AS rownum,TbDetail.strGuid,
TbDetail.strDetectorId, TbDetail.fltTemperature, TbDetail.dtSysTime FROM TbDetail where
(TbDetail.strGuid in(SELECT strGuid
FROM TbDetail a
WHERE (dtSysTime IN
(SELECT MAX(dtSysTime) AS dtSysTime
FROM TbDetail b
WHERE (a.strDetectorId = b.strDetectorId) and (a.strAddress=b.strAddress)
GROUP BY strDetectorId,strAddress)) and (a.strAddress='0001') ))) AS T
WHERE rownum BETWEEN 1 AND 10 //使用ROW_NUMBER()进行分页查询
strGuid strDetectorId fltTemperature dtSysTime strAddress
887c80e ... 1 30 2009-8-11 17:04:35 0001
887c80e ... 1 27.5 2009-8-12 13:30:00 0001
887c80e ... 1 27.9 2009-8-13 17:48:56 0001
887c80e ... 1 27.3 2009-8-14 14:33:06 0001
887c80e ... 2 28.1 2009-8-15 9:25:19 0001
887c80e ... 2 28.1 2009-8-15 9:27:15 0001
887c80e ... 2 28 2009-8-17 14:32:41 0001
要把“每种仪器”的“最大时间”和“最大时间对应的温度”查询出来,请问怎么解决? 以下是我的SQL语句,但是有的时候查出来的数据不对。请高手帮我分析下? SELECT *
FROM (SELECT ROW_NUMBER() OVER(ORDER BY TbDetail.strDetectorId) AS rownum,TbDetail.strGuid,
TbDetail.strDetectorId, TbDetail.fltTemperature, TbDetail.dtSysTime FROM TbDetail where
(TbDetail.strGuid in(SELECT strGuid
FROM TbDetail a
WHERE (dtSysTime IN
(SELECT MAX(dtSysTime) AS dtSysTime
FROM TbDetail b
WHERE (a.strDetectorId = b.strDetectorId) and (a.strAddress=b.strAddress)
GROUP BY strDetectorId,strAddress)) and (a.strAddress='0001') ))) AS T
WHERE rownum BETWEEN 1 AND 10 //使用ROW_NUMBER()进行分页查询
--按某一字段分组取最大(小)值所在行的数据
--(爱新觉罗.毓华(十八年风雨,守得冰山雪莲花开) 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,a.val
/*
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 , a.val
/*
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)
*/
If not object_id('[tb]') is null
Drop table [tb]
Go
Create table [tb]([strGuid] varchar(10),[strDetectorId] int,fltTemperature numeric(8,1), dtSysTime datetime,strAddress varchar(4))
Insert [tb]
Select '887c80e001',1,30,'2009-8-11 17:04:35',0001 union all
Select '887c80e002',1,27.5,'2009-8-12 13:30:00',0001 union all
Select '887c80e003',1,27.9,'2009-8-13 17:48:56',0001 union all
Select '887c80e004',1,27.3,'2009-8-14 14:33:06',0001 union all
Select '887c80e005',2,28.1,'2009-8-15 9:25:19',0001 union all
Select '887c80e006',2,28.1,'2009-8-15 9:27:15',0001 union all
Select '887c80e007',2,28,'2009-8-17 14:32:41',0001
Go-->SQL查询如下:
select t.* from Tb t where not exists(select 1 from Tb where strDetectorId = t.strDetectorId and strAddress = t.strAddress and dtSysTime > t.dtSysTime)
顺便问一下:括号内的select 1 的1是什么意思,可以换成别的符合吗?