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