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Mysql應(yīng)用MySQL 刪除數(shù)據(jù)庫中重復(fù)數(shù)據(jù)方法小結(jié)

作者：VEPHP   時間 2017-10-22

《Mysql應(yīng)用MySQL 刪除數(shù)據(jù)庫中重復(fù)數(shù)據(jù)方法小結(jié)》要點：
本文介紹了Mysql應(yīng)用MySQL 刪除數(shù)據(jù)庫中重復(fù)數(shù)據(jù)方法小結(jié)，希望對您有用。如果有疑問，可以聯(lián)系我們。

剛開始,根據(jù)我的想法,這個很簡單嘛,上sql語句MYSQL必讀

delete from zqzrdp where tel in (select min(dpxx_id) from zqzrdp group by tel having count(tel)>1);

執(zhí)行,報錯!!~!~MYSQL必讀

MYSQL必讀

異常意為：你不能指定目標表的更新在FROM子句.傻了,MySQL 這樣寫,不行,讓人郁悶.MYSQL必讀

難倒只能分步操作,蛋疼MYSQL必讀

以下是網(wǎng)友寫的,同樣是坑爹的代碼,我機器上運行不了.MYSQL必讀

1. 查詢需要刪除的記錄,會保留一條記錄.MYSQL必讀

select a.id,a.subject,a.RECEIVER from test1 a left join (select c.subject,c.RECEIVER ,max(c.id) as bid from test1 c where status=0 GROUP BY RECEIVER,SUBJECT having count(1) >1) b on a.id< b.bid where a.subject=b.subject and a.RECEIVER = b.RECEIVER and a.id < b.bid

2. 刪除重復(fù)記錄,只保留一條記錄.注意,subject,RECEIVER 要索引,否則會很慢的.MYSQL必讀

delete a from test1 a, (select c.subject,c.RECEIVER ,max(c.id) as bid from test1 c where status=0 GROUP BY RECEIVER,SUBJECT having count(1) >1) b where a.subject=b.subject and a.RECEIVER = b.RECEIVER and a.id < b.bid;

3. 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MYSQL必讀

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

4. 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MYSQL必讀

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)

5.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MYSQL必讀

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)

看來想偷懶使用一句命令完成這個事好像不太顯示,還是老老實實的分步處理吧,思路先建立復(fù)制一個臨時表,然后對比臨時表內(nèi)的數(shù)據(jù),刪除主表里的數(shù)據(jù)MYSQL必讀

alter table tableName add autoID int auto_increment not null; 
create table tmp select min(autoID) as autoID from tableName group by Name,Address; 
create table tmp2 select tableName.* from tableName,tmp where tableName.autoID = tmp.autoID; 
drop table tableName; 
rename table tmp2 to tableName;

《Mysql應(yīng)用MySQL 刪除數(shù)據(jù)庫中重復(fù)數(shù)據(jù)方法小結(jié)》是否對您有啟發(fā)，歡迎查看更多與《Mysql應(yīng)用MySQL 刪除數(shù)據(jù)庫中重復(fù)數(shù)據(jù)方法小結(jié)》相關(guān)教程，學(xué)精學(xué)透。維易PHP學(xué)院為您提供精彩教程。

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