求SQL语句:删除zcm和xlrq完全相同的行中多余的,只留下一行(任一行)例子:
由表(红色行为重复多余行)
zcm xlrq sl
01 2008-1-1 1
01 2008-1-1 2
01 2008-2-1 3
02 2008-1-1 4
02 2008-1-2 5
03 2008-1-1 6
03 2008-1-1 7
03 2008-1-1 8查询出表
zcm xlrq sl
01 2008-1-1 1
01 2008-2-1 3
02 2008-1-1 4
02 2008-1-2 5
03 2008-1-1 6
由表(红色行为重复多余行)
zcm xlrq sl
01 2008-1-1 1
01 2008-1-1 2
01 2008-2-1 3
02 2008-1-1 4
02 2008-1-2 5
03 2008-1-1 6
03 2008-1-1 7
03 2008-1-1 8查询出表
zcm xlrq sl
01 2008-1-1 1
01 2008-2-1 3
02 2008-1-1 4
02 2008-1-2 5
03 2008-1-1 6
(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')
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 object_id('tempdb.dbo.#T') is not null drop table #T
create table #T (zcm varchar(2),xlrq datetime,sl int)
insert into #T
select '01','2008-1-1',1 union all
select '01','2008-1-1',2 union all
select '01','2008-2-1',3 union all
select '02','2008-1-1',4 union all
select '02','2008-1-2',5 union all
select '03','2008-1-1',6 union all
select '03','2008-1-1',7 union all
select '03','2008-1-1',8
go
select zcm,xlrq,min(sl) sl
from #T
group by zcm,xlrq
go
drop table #T/*
zcm xlrq sl
---- ----------------------- -----------
01 2008-01-01 00:00:00.000 1
02 2008-01-01 00:00:00.000 4
03 2008-01-01 00:00:00.000 6
02 2008-01-02 00:00:00.000 5
01 2008-02-01 00:00:00.000 3(5 row(s) affected)*/
if object_id('tempdb.dbo.#T') is not null drop table #T
create table #T (zcm varchar(2),xlrq datetime,sl int)
insert into #T
select '01','2008-1-1',1 union all
select '01','2008-1-1',2 union all
select '01','2008-2-1',3 union all
select '02','2008-1-1',4 union all
select '02','2008-1-2',5 union all
select '03','2008-1-1',6 union all
select '03','2008-1-1',7 union all
select '03','2008-1-1',8
go
select *
from #T as t
where not exists(select * from #T where zcm=t.zcm and xlrq=t.xlrq and sl<t.sl)
go
drop table #T
if not object_id('Tempdb..#T') is null
drop table #T
Go
Create table #T([zcm] int,[xlrq] Datetime,[sl] int)
Insert #T
select 01,'2008-1-1',1 union all
select 01,'2008-1-1',2 union all
select 01,'2008-2-1',3 union all
select 02,'2008-1-1',4 union all
select 02,'2008-1-2',5 union all
select 03,'2008-1-1',6 union all
select 03,'2008-1-1',7 union all
select 03,'2008-1-1',8
Godelete #T where sl in(
select sl from(
select rowid=row_number() over(partition by zcm,xlrq order by zcm),* from #T)b
where rowid>1)
lz可以看看我的博客,里面有两篇讨论删除相同行的文章
if object_id('tempdb.dbo.#T') is not null drop table #T
create table #T (zcm varchar(2),xlrq datetime,sl int)
insert into #T
select '01','2008-1-1',1 union all
select '01','2008-1-1',2 union all
select '01','2008-2-1',3 union all
select '02','2008-1-1',4 union all
select '02','2008-1-2',5 union all
select '03','2008-1-1',6 union all
select '03','2008-1-1',7 union all
select '03','2008-1-1',8
go
with cte as
(
select rid=row_number() over(partition by zcm,xlrq order by sl),*
from #T
)
delete from cte where rid>1select * from #T
go
drop table #T/*
zcm xlrq sl
---- ----------------------- -----------
01 2008-01-01 00:00:00.000 1
01 2008-02-01 00:00:00.000 3
02 2008-01-01 00:00:00.000 4
02 2008-01-02 00:00:00.000 5
03 2008-01-01 00:00:00.000 6(5 row(s) affected)
*/