SQL删除,重复数据只保留一条

 　　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

　　upd

　　where peopleId in (select peopleId from vitae group by peopleId