sql删除重复记录
sql删除重复记录
王念博客 发表于2年前
sql删除重复记录
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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


mysql需要 把查询出来的结果再 select一下

比如 select * from t id in (select id form (select min(id) id from t group by no having count(no)>1)) )


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