DELETE FROM `logs` WHERE wangzhi='www.juhutang.com' and id<>101072; 上面这段代码的意思为 删除表logs中 所有字段wangzhi含内容为www.juhutang.com的数据.但是不删除同表中 id 是101072 的这条数据. 当然了 我是新手,这条语句可能与标题不是那么完善, 希望大牛解答,删除表中所有数据,保留最近的一条 或者说只保留主键ID最大的一条. 这语句如何写.
/* ROWID是行ID,通过它一定可以定位到r任意一行的数据记录 ROWID DNAME DEPTNO LOC ------------------ ---------------------------- ---------- ---------- AAASSUAAEAAAAIbAAA ACCOUNTING 10 NEW YORK AAASSUAAEAAAAIbAAB RESEARCH 20 DALLAS AAASSUAAEAAAAIbAAC SALES 30 CHICAGO AAASSUA
1.查询表中重复数据.select * from peoplewhere peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)2.删除表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断,只留有rowid最小的记录delete from people where peopleId in (select peopleId
create table test1( id number, name varchar2(20) ); ,'jack'); ,'jack'); ,'peter'); ,'red'); insert into test1 values(5,'green'); insert into test1 values(6,'green'); 一 查询表中重复数据 1. 使用exists select a.* from test1 a where exists ( select name from ( se
delete from zqzrdp where tel in (select min(dpxx_id) from zqzrdp group by tel having count(tel)>1); 运行,报错 watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvdTAxMTU5ODUyOQ==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"
select distinct * into #tmptable from tablename drop table tablename select * into tablename from #tmptable drop #tmptable 思路:把表中重复的数据祛重之后放入临时表中,第二步删掉表中原有的数据,接着把临时表中的数据放入原表中,最后删掉临时表
1. 查询需要删除的记录,会保留一条记录. 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.R
例子:表名 Paper .通过字段PaperID查找重复数据. 1 --查询某表中重复的数据 select * from Paper group by PaperID having count(*)>1; 2--删除重复行数,只剩不重复的记录(rowid为sqlite自带字段) delete from Paper where Paper.rowid not in (select MAX(Paper.rowid) from Paper group by PaperID);
语句: delete from table1 where id not in (select minid from (select min(id) as minid from table1 group by field1) b); 翻译成中文就是: 删除,“table1”中,id 不在此范围的所有记录.此范围是,筛选出,以field1分组的,所有组别中id的最小的一个. 更直接点就是,以field1分组,选出分组中id最小的一条记录,然后剩下的全部删除. 理解不正确的话,请指点一二.
方法一:利用游标,但要注意主字段或标识列 declare @max integer,@id integer open cur_rows fetch cur_rows into @id,@max begin set rowcount @max delete from 表名 where 主字段 = @id fetch cur_rows into @id,@max end close cur_rows 方法二:利用临时表处理 方法二 有两个意义上的重复记录,一是完全重复的记录,也即所有字段均重复的记录
采集数据的时候,由于先期对页面结构的分析不完善,导致采漏了一部分数据.完善代码之后重新运行 Scrapy,又采集了一些重复的数据,搜了下删除重复数据的方法. N.B. 删除数据表的重复数据时,请先备份数据表. 方法一 # 保留主键 ID 较小的那条记录 DELETE n1 FROM names n1, names n2 WHERE n1.id > n2.id AND n1.name = n2.name # 保留主键 ID 较大的那条记录 DELETE n1 FROM names n1, name