oracle sql去重

最新推荐文章于 2025-01-11 10:31:56 发布

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最新推荐文章于 2025-01-11 10:31:56 发布

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分类专栏：数据库文章标签： sql 数据库 oracle

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本文介绍了多种SQL查询和删除语句，用于在数据库表中查找和删除重复记录。方法包括根据单个字段和多个字段判断重复，并保留特定条件的记录，如保留rowid最小的记录。此外，还提供了更新字段内容以删除特定字符的示例。

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--1、删除掉重复项只保留一条
delete from dept
 where rowid not in
       (select max(rowid) mrid from dept group by deptno, dname, loc)
--2、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)
--3、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)
--4、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)
--5、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)
--6、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)
--7.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%'
--8.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'
--9.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)