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sql 删除重复记录语句收藏

sql 删除重复记录语句收藏
删除重复记录的题目。现给出解决此题的答案,如下:

select distinct * into Temp from Student
truncate table Student
insert Student select * from Temp
drop table Temp
--至此删除了重复的数据。
--显示删除后的结果
select * from student
思路是先查询出没有重复的数据保存到一个临时的表Temp里面,然后再用truncate关键字删除目标表的数据内容,最后使用drop命令删除Temp表即可。


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斐波那契数列非递归的C#代码解法如下:用数学里面的通项

static Int64 Fib(Int64 n)
{
     int first, second, third;
     first = second = third = 1;
     if (n==1||n==2)
     {
          return 1;
     }
     for (int i = 3; i <= n; i++)
     {
         first = second + third;
         third = second;
         second = first;
     }
     return first;
}
Fibonacci(斐波那契)序列:
Fib(n) = Fib(n - 1) + Fib(n - 2), n>1, Fib(1) = Fib(2) = 1
即:序列的第一和第二项是1,从第三项开始,后一项是前两项的和。
序列的前8项是:
1, 1, 2, 3, 5, 8, 13, 21


更多更好方法

若想将姓名、身份证号、住址这三个字段完全相同的记录查询出来
select   p1.*   from   persons   p1,persons   p2   where   p1.id<>p2.id   and   p1.cardid   =   p2.cardid   and   p1.pname   =   p2.pname   and   p1.address   =   p2.address


可以实现上述效果.

几个删除重复记录的SQL语句
 
1.用rowid方法

2.用group by方法

3.用distinct方法

1。用rowid方法

据据oracle带的rowid属性,进行判断,是否存在重复,语句如下:

查数据:

     select * from table1 a where rowid !=(select   max(rowid) 
     from table1 b where a.name1=b.name1 and a.name2=b.name2......)

删数据:

    delete   from table1 a where rowid !=(select   max(rowid) 
     from table1 b where a.name1=b.name1 and a.name2=b.name2......)

2.group by方法

查数据:

  select count(num), max(name) from student --列出重复的记录数,并列出他的name属性
  group by num
  having count(num) >1 --按num分组后找出表中num列重复,即出现次数大于一次

删数据:

  delete from student
  group by num
  having count(num) >1
  这样的话就把所有重复的都删除了。

3.用distinct方法 -对于小的表比较有用

 

create table table_new as   select distinct *   from table1 minux
truncate table table1;
insert into table1 select * from table_new;

查询及删除重复记录的方法大全

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)


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)


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)

 

补充:数据库,Mssql
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