有一个表,如下:(简化过)表名 abc
内容如下:
列 name number email home
记录 cx1 123455 cx@cx ccc
cx2 123455 cx@cx ccc
cx3 123455 cx@cx ccc
cx4 123456 cx@cx ccc
cx 123456 cx@cx ccc
cx 123456 cx@cx ccc
cx 123457 cx@cx ccc
要求是这样的,提取的记录要符合如下规则:
多条有相同的号码的记录只显示一条(任意一条即可)。
目的就是让号码唯一,至于其他列名是否唯一都不重要,
最后要显示提取出记录的所有字段内容。
内容如下:
列 name number email home
记录 cx1 123455 cx@cx ccc
cx2 123455 cx@cx ccc
cx3 123455 cx@cx ccc
cx4 123456 cx@cx ccc
cx 123456 cx@cx ccc
cx 123456 cx@cx ccc
cx 123457 cx@cx ccc
要求是这样的,提取的记录要符合如下规则:
多条有相同的号码的记录只显示一条(任意一条即可)。
目的就是让号码唯一,至于其他列名是否唯一都不重要,
最后要显示提取出记录的所有字段内容。
if object_id('[abc]') is not null drop table [abc]
go
create table [abc]([name] varchar(3),[number] int,[email] varchar(5),[home] varchar(3))
insert [abc]
select 'cx1',123455,'cx@cx','ccc' union all
select 'cx2',123455,'cx@cx','ccc' union all
select 'cx3',123455,'cx@cx','ccc' union all
select 'cx4',123456,'cx@cx','ccc' union all
select 'cx',123456,'cx@cx','ccc' union all
select 'cx',123456,'cx@cx','ccc' union all
select 'cx',123457,'cx@cx','ccc'
---查询---
select name,number,email,home
from
(select rn=row_number() over(partition by number order by getdate()),* from abc) t
where rn=1---结果---
name number email home
---- ----------- ----- ----
cx1 123455 cx@cx ccc
cx4 123456 cx@cx ccc
cx 123457 cx@cx ccc(3 行受影响)
(
select distinct * from abc
) m where not exists(select 1 from
(
select distinct * from abc
) n where number = t.number and name < t.name)
insert [abc]
select 'cx1',123455,'cx@cx','ccc' union all
select 'cx2',123455,'cx@cx','ccc' union all
select 'cx3',123455,'cx@cx','ccc' union all
select 'cx4',123456,'cx@cx','ccc' union all
select 'cx',123456,'cx@cx','ccc' union all
select 'cx',123456,'cx@cx','ccc' union all
select 'cx',123457,'cx@cx','ccc'--由于你存在完全相同的记录,需要如下:select m.* from
(
select distinct * from abc
) m where not exists(select 1 from
(
select distinct * from abc
) n where number = m.number and name < m.name)drop table abc/*
name number email home
---- ----------- ----- ----
cx1 123455 cx@cx ccc
cx 123456 cx@cx ccc
cx 123457 cx@cx ccc(所影响的行数为 3 行)*/
--(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)
*/
--> 数据库版本:
--> Microsoft SQL Server 2008 (RTM) - 10.0.1600.22
--> 测试数据:[TB]
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[TB]')
AND type in (N'U'))
DROP TABLE [TB]
GO---->建表
create table [TB]([name] varchar(3),[number] int,[email] varchar(5),[home] varchar(3))
insert [TB]
select 'cx1',123455,'cx@cx','ccc' union all
select 'cx2',123455,'cx@cx','ccc' union all
select 'cx3',123455,'cx@cx','ccc' union all
select 'cx4',123456,'cx@cx','ccc' union all
select 'cx',123456,'cx@cx','ccc' union all
select 'cx',123456,'cx@cx','ccc' union all
select 'cx',123457,'cx@cx','ccc'
GO--> 查询结果
alter table TB add dd varchar(20)
godeclare @i int,@fff varchar(20)=''
set @i=1
update [TB]
set dd=@i, @i=case when [number]!=@fff then 0 else @i+1 end ,@fff=[number]
goSELECT * FROM [TB]
where dd=0alter table TB drop column dd--> 删除表格
--DROP TABLE [TB]