SQL删除重复数据只保留一条

来源：互联网发布：sql 查询一天内的数据编辑：程序博客网时间：2024/05/23 12:43

用SQL语句,删除掉重复项只保留一条

在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢
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   peopleName in (select peopleName    from people group by peopleName      having count(peopleName) > 1)
and   peopleId not in (select min(peopleId) from people group by peopleName     having count(peopleName)>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)

6.消除一个字段的左边的第一位：

update tableName set [Title]=Right([Title],(len([Title])-1)) where Title like '村%'

7.消除一个字段的右边的第一位：

update tableName set [Title]=left([Title],(len([Title])-1)) where Title like '%村'

8.假删除表中多余的重复记录（多个字段），不包含rowid最小的记录
update vitae set ispass=-1
where peopleId in (select peopleId from vitae group by peopleId

============================================================================================

删除重复数据只保存一条--ms sql及oracle实现方法

ms sql方法：

declare @sss table (ID int, Name varchar(10), address varchar(10))

insert into @sss select 1,'小王','重庆'

insert into @sss select 2,'小张','北京'

insert into @sss select 3,'小明','上海'

insert into @sss select 4,'小红','重庆'

insert into @sss select 5,'小李','重庆'

insert into @sss select 6,'小白','北京'

insert into @sss select 7,'小红','上海'

insert into @sss select 8,'小红','重庆'

delete from @sss where id not in(select min(id) from @sss group by name,address)

------------------------------------------------------------------------------------------------------------

oracle方法：

SQL> CREATE TABLE test_delete(

2 name varchar(10),

3 value INT

4 );

表已创建。

SQL> INSERT INTO test_delete

2 SELECT '张三', 100 FROM dual

3 UNION ALL SELECT '张三', 100 FROM dual

4 UNION ALL SELECT '李四', 80 FROM dual

5 UNION ALL SELECT '王五', 80 FROM dual

6 UNION ALL SELECT '王五', 80 FROM dual

7 UNION ALL SELECT '赵六', 90 FROM dual

8 UNION ALL SELECT '赵六', 70 FROM dual;

已创建7行。

SQL> SELECT

2 ROWID,

3 name,

4 value

5 FROM

6 test_delete;

ROWID NAME VALUE

------------------ ---------- ----------

AAAM2mAAGAAAAOXAAA 张三 100

AAAM2mAAGAAAAOXAAB 张三 100

AAAM2mAAGAAAAOXAAC 李四 80

AAAM2mAAGAAAAOXAAD 王五 80

AAAM2mAAGAAAAOXAAE 王五 80

AAAM2mAAGAAAAOXAAF 赵六 90

AAAM2mAAGAAAAOXAAG 赵六 70

已选择7行。

SQL> DELETE

2 test_delete

3 WHERE

4 (name, value)

5 IN (SELECT

6 name, value

7 FROM

8 test_delete

9 GROUP BY

10 name, value

11 HAVING COUNT(1) > 1)

12 AND rowid NOT IN

13 (SELECT

14 MIN(rowid)

15 FROM

16 test_delete

17 GROUP BY

18 name, value

19 HAVING

20 COUNT(1) > 1);

已删除2行。