SQL重复查询及触发器的使用

 2007.07.13  jackey  好东西

 

SQL重复查询及触发器的使用

1、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断

select * from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
例二：
select * from testtable
where numeber in (select number from people group by number having count(number) > 1 )
可以查出testtable表中number相同的记录

 

select * from tYHXGX
where SJHM in (select SJHM from tYHXGX group by SJHM having count(SJHM) > 1 )

 

2、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录
delete from people
where peopleId in (select peopleId from people group by peopleId   having count(peopleId) > 1)
and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>1)

 

delete from tYHXGX1
where SJHM in (select SJHM from tYHXGX1 group by SJHM   having count(SJHM) > 1)
and id not in (select min(id) from tYHXGX1 group by SJHM having count(SJHM )>1)

 

3、查找表中多余的重复记录（多个字段）
select * from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录
delete from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录
select * from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

(二)
比方说
在A表中存在一个字段“name”，
而且不同记录之间的“name”值有可能会相同，
现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；

Select Name,Count(*) From A Group By Name Having Count(*) > 1

 

Select SJHM,Count(*) From tYHXGX  Group By SJHM Having Count(*) > 1

 

如果还查性别也相同大则如下:
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1

(三)
方法一

declare @max integer,@id integer

declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having count(*) >； 1

open cur_rows

fetch cur_rows into @id,@max

while @@fetch_status=0

begin

select @max = @max -1

set rowcount @max

delete from 表名 where 主字段 = @id

fetch cur_rows into @id,@max

end

close cur_rows

set rowcount 0

　　方法二

　　有两个意义上的重复记录，一是完全重复的记录，也即所有字段均重复的记录，二是部分关键字段重复的记录，比如Name字段重复，而其他字段不一定重复或都重复可以忽略。

　　1、对于第一种重复，比较容易解决，使用

select distinct * from tableName

　　就可以得到无重复记录的结果集。

　　如果该表需要删除重复的记录（重复记录保留1条），可以按以下方法删除

select distinct * into #Tmp from tableName

drop table tableName

select * into tableName from #Tmp

drop table #Tmp

　　发生这种重复的原因是表设计不周产生的，增加唯一索引列即可解决。

　　2、这类重复问题通常要求保留重复记录中的第一条记录，操作方法如下

　　假设有重复的字段为Name,Address，要求得到这两个字段唯一的结果集

select identity(int,1,1) as autoID, * into #Tmp from tableName

select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID

select * from #Tmp where autoID in(select autoID from #tmp2)

　　最后一个select即得到了Name，Address不重复的结果集（但多了一个autoID字段，实际写时可以写在select子句中省去此列）

(四)
查询重复

select * from tablename where id in (

select id from tablename

group by id

having count(id) > 1

)

另：

创建触发器和使用示例(于海涛 老师的实验课)


1、数据表的建立

use login

create table voteMaster   -----主表
(
voteId int primary key,    --编号
voteTitle varchar(100) not null,   ---投票的项目
voteSum int default 0   --总票数，默认为0
)
insert into voteMaster values(1,'选举工会主席',0)
insert into voteMaster values(2,'对网站的建议',0)

create table voteDetails    ---从表
(
voteId int foreign key references voteMaster(voteId),----外键 约束
voteDetailsId int not null,
voteItem varchar(20) not null,
votNum int default 0,
primary key(voteId,voteDetailsId)          ----连合主键
)

insert into voteDetails values(1,1,'于海涛',0)
insert into voteDetails values(1,2,'王小刚',0)
insert into voteDetails values(1,3,'张老三',0)

insert into voteDetails values(2,1,'非常好',0)
insert into voteDetails values(2,2,'好',0)
insert into voteDetails values(2,3,'一般',0)
insert into voteDetails values(2,4,'需要改进',0)

2、触发器的创建

create trigger updateMaster   -----创建触发器
on voteDetails     -----触发器所建的表
for update         -----触发器的条件
as
begin
           update voteMaster set voteSum=voteSum+1 where voteId=(select top 1 voteid from inserted)
end

最终效果：

你只要对voteDetails 内votNum的数据进行更新，那么主表voteMaster 的voteSum就会加1，从而实现了对投票的总数的统计的实现。

注意:    select top 1 voteid from deleted

          inserted表   deleted表
insert 新插入的行 空
update 数据库受到影响的行在更新之后的新值 数据库受到影响的行在更新之前的旧值
delete 空 删除的行

 

 

 

 

当你想自动更新数据库的时候 无论数据库怎样更新,插入新数据也好,自动在后面添加你想添加的东西

create trigger trig_notic_UI
on notic for insert,update
as
update notic set memo=memo+'<dcboy>'
where id in(select id from inserted)
go

/*
trig_notic_UI   触发器名称 自定义
notic 需要触发的表名
memo 需要更新的字段
id   是主键
*/