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(gè)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(gè)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(gè)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(gè)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(gè)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(gè)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(gè)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(gè)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