2011年計(jì)算機(jī)等考二級VB輔導(dǎo)知識技巧總結(jié)(12)

　　查詢及刪除重復(fù)記錄的方法

　　(一)

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

　　and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>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)

　　(二)

　　比方說

　　在A表中存在一個(gè)字段“name”，

　　而且不同記錄之間的“name”值有可能會(huì)相同，

　　現(xiàn)在就是需要查詢出在該表中的各記錄之間，“name”值存在重復(fù)的項(xiàng);

　　Select Name,Count(*) From A Group By Name Having Count(*) > 1

　　如果還查性別也相同大則如下:

　　Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1

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