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在 sql 中,可以使用 select 語(yǔ)句刪除重復(fù)數(shù)據(jù),語(yǔ)法為:“select * from 字段 where 字段 id in (select 字段 id from 字段 group by 字段 having count( 字段 id) 1)”。
本教程操作環(huán)境:windows7 系統(tǒng)、mysql8.0 版本、Dell G3 電腦。
用 SQL 語(yǔ)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(yǔ)句, 刪除掉重復(fù)的呢
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(lái)判斷
select * from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) 1)
擴(kuò)展:
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(lái)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)
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)
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)
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)
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 %
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
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=-1where peopleId in (select peopleId from vitae group by peopleId
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