Oracle 删除重复数据只留一条

查询及删除重复记录的SQL语句

1、查找表中多余的重复记录，重复记录是根据单个字段（Id）来判断 

select * from 表 

where Id in (select Id from 表 group byId having count(Id) > 1)

 

2、删除表中多余的重复记录，重复记录是根据单个字段（Id）来判断，只留有rowid最小的记录 

DELETE from 表 WHERE id IN ( SELECT id FROM 表 GROUP BY id HAVING COUNT(id) > 1) 

                     AND ROWID NOT IN (SELECT MIN(ROWID) FROM 表 GROUP BY id HAVING COUNT(*) > 1);

 

3、查找表中多余的重复记录（多个字段） 

select * from 表 a where (a.Id,a.seq) in(select Id,seq from 表 group by Id,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 表 a 

where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) 

      and rowid not in (select min(rowid) from 表 group by Id,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 表 a 

where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) 

and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)

如下例子
--单个字段
create table Student(

ID NUMBER(8) PRIMARY KEY,

NAME VARCHAR(50));

INSERT INTO Student (ID,NAME) VALUES(100001,'Zhang San');

INSERT INTO Student (ID,NAME) VALUES(100002,'Li Si');

INSERT INTO Student (ID,NAME) VALUES(100003,'Zhang San');

INSERT INTO Student (ID,NAME) VALUES(100004,'Wang Wu');

INSERT INTO Student (ID,NAME) VALUES(100005,'Li Si');

select * from Student;

select rowid,stu.* from Student stu where stu.name in(select name from Student group by name having count(name)>1);

delete from Student where name in(select name from Student group by name having count(name)>1)

and ROWID NOT IN(SELECT MIN(ROWID)FROM Student group by name  having count(name)>1)；

--两个字段
create table Student_Subject(

STU_ID NUMBER(8) NOT NULL,

SUB_ID NUMBER(8) NOT NULL);

INSERT INTO Student_Subject (STU_ID,SUB_ID) VALUES(10001,10);

INSERT INTO Student_Subject (STU_ID,SUB_ID) VALUES(10002,10);

INSERT INTO Student_Subject (STU_ID,SUB_ID) VALUES(10001,10);

INSERT INTO Student_Subject (STU_ID,SUB_ID) VALUES(10001,11);

INSERT INTO Student_Subject (STU_ID,SUB_ID) VALUES(10001,12);

INSERT INTO Student_Subject (STU_ID,SUB_ID) VALUES(10002,10);

INSERT INTO Student_Subject (STU_ID,SUB_ID) VALUES(10002,11);

SELECT * FROM Student_Subject order by STU_ID,SUB_ID;

--查找表中多余的重复记录(两个字段)

SELECT ROWID,ss.*

FROM Student_Subject ss

where (ss.STU_ID,ss.SUB_ID) in

         (select STU_ID,SUB_ID from Student_Subject group by STU_ID,SUB_ID having count(*)>1);

--查找表中多余的重复记录（两个字段），不包含rowid最小的记录

SELECT ROWID,ss.*

FROM Student_Subject ss

WHERE (ss.STU_ID,ss.SUB_ID)in (select STU_ID,SUB_ID

                               from Student_Subject

                               group by STU_ID,SUB_ID

                               having count(*)>1)

      and ROWID NOT IN(select min(ROWID) from Student_Subject group by STU_ID,SUB_ID having count(*)>1)

ORDER BY ss.STU_ID,ss.SUB_ID;

--删除表中多余的重复记录（两个字段），只留有rowid最小的记录

DELETE FROM Student_Subject

WHERE (STU_ID,SUB_ID) in (select STU_ID,SUB_ID

                         from Student_Subject

                         group by STU_ID,SUB_ID

                         having count(*)>1)

      and ROWID NOT IN (select min(ROWID) from Student_Subject group by STU_ID,SUB_ID having count(*)>1);