从身份证删除SQL Server 2012表的重复记录

Question

我想复制一个场景，我需要从表中删除除了一个表的所有重复的行。但所有行都有唯一的标识列。

为了使事情更容易，我创建了一个小测试表学生，脚本如下。

create table student 
(
    id int, 
    rollno int, 
    name varchar(50), 
    course varchar(50) 
) 
GO 

insert into student values(1,1335592,'john','biology') 
insert into student values(2,1335592,'john','biology') 
insert into student values(3,1335592,'john','biology') 
insert into student values(4,1335592,'john','biology') 
insert into student values(5,1335593,'peter','biology') 
insert into student values(6,1335593,'peter','biology') 
insert into student values(7,1335593,'peter','biology') 
GO 

select * from student 

这将生成如下表格。

id rollno name course 
1 1335592 john biology 
2 1335592 john biology 
3 1335592 john biology 
4 1335592 john biology 
5 1335593 peter biology 
6 1335593 peter biology 
7 1335593 peter biology 

我想在结果集中保留ID为'1'和'5'的记录并删除其他所有内容。有没有办法做到这一点？

所有帮助将不胜感激。

感谢 Shammas

Answer 1

这是简单的查询

Delete from student 
where id not in (select min(id) 
       from student 
       group by rollno, name, course) 

Answer 2

使用CTE。

查询

;with cte as 
(
    select rn=row_number() over 
    (
    partition by rollno,name,course 
    order by id 
),* 
    from student 
) 
delete from cte 
where rn > 1; 

Fiddle demo

Answer 3

可以使用 DENSE_RANK， ROW_NUMBER，RANK

这些all'll会给你结果。

尝试：

create table student 
(id int, 
rollno int, 
name varchar(50), 
course varchar(50) 
) 
GO 

insert into student values(1,1335592,'john','biology') 
insert into student values(2,1335592,'john','biology') 
insert into student values(3,1335592,'john','biology') 
insert into student values(4,1335592,'john','biology') 
insert into student values(5,1335593,'peter','biology') 
insert into student values(6,1335593,'peter','biology') 
insert into student values(7,1335593,'peter','biology') 
GO 



;with cte as 
(
    select rn=row_number() over 
    (
    partition by rollno,name,course 
    order by id 
),* 
    from student 
) 
select * from cte where rn=1 

;with cte2 as 
(
    select rn=RANK() over 
    (
    partition by rollno,name,course 
    order by id 
),* 
    from student 
) 
select * from cte2 where rn=1 

;with cte3 as 
(
    select rn=Dense_RANK() over 
    (
    partition by rollno,name,course 
    order by id 
),* 
    from student 
) 
select * from cte3 where rn=1 

见Difference between ROW_NUMBER(), RANK() and DENSE_RANK()

Answer 4

DELETE s 
FROM student s 
JOIN student s2 ON s.course = s2.course 
    AND s.NAME = s2.NAME 
    AND s.rollno = s2.rollno 
WHERE s2.id < s.id