用SQL語句，刪除掉重復(fù)項(xiàng)只保留一條

在幾千條記錄里，存在著些相同的記錄，如何能用SQL語句，刪除掉重復(fù)的呢

1、查找表中多余的重復(fù)記錄，重復(fù)記錄是根據(jù)單個字段(peopleId)來判斷

select * from people

where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

2、刪除表中多余的重復(fù)記錄，重復(fù)記錄是根據(jù)單個字段(peopleId)來判斷，只留有rowid最小的記錄

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、查找表中多余的重復(fù)記錄(多個字段)

select * from vitae a

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

4、刪除表中多余的重復(fù)記錄(多個字段)，只留有rowid最小的記錄

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、查找表中多余的重復(fù)記錄(多個字段)，不包含rowid最小的記錄

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.消除一個字段的左邊的第一位：

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

7.消除一個字段的右邊的第一位：

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

8.假刪除表中多余的重復(fù)記錄(多個字段)，不包含rowid最小的記錄

update vitae set ispass=-1

where peopleId in (select peopleId from vitae group by peopleId

alter table mytable drop index mdl_tag_use_ix;//mdl_tag_use_ix是上表查出的索引名，key_name

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