用SQL语句,删除掉重复项只保留一条 在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢 1.查找表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断 select * from people where 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

--创建测试表 CREATE TABLE TEST ( DEPTNO ), DNAME ), LOC ) ); --插入测试数据 , 'test1', 'test2'); , 'test1', 'test2'); , 'test2', 'test3'); , 'test2', 'test3'); --查询所有记录 SELECT * FROM TEST; --查询重复的记录 SELECT * FROM TEST WHERE deptno IN( ) --查询重复记录-1条记录 SELECT * F

SQL:删除重复数据,只保留一条用SQL语句,删除掉重复项只保留一条在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢 1.查找表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断 ) 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 ) ) 3.查找表中多余的重复记录(多个字段) ) 4.删除表中多余的重复记录(多个字段),只留有rowid最小的记录 ) ) 5.查找表中多余的重复记录(多个字段),不包

情景: 我们的数据库中可能会存在很多因各种原因而重复的记录,我们需要对这些重复的记录进行删除,每组组重复的记录只保留一条就行 例如我们有这么个表:两个框框都是有重复记录的,红框和绿框都只需要留下一条,其他的都干掉. 前提: 1:每天记录都要有一个唯一id 2:每组重复的记录要有字段能进行分组,例如上面我们按name.class.age.score相同的就是一组. 数据宝贵,请先备份!!! 数据宝贵,请先备份!!! 数据宝贵,请先备份!!! 放上整条SQL: DELETE FROM "t_hw_t

--查找表中多余的重复记录select * from code_xz where code in (select code from code_xz group by code having count(1)>1) --删除表中多余的重复记录,只留有pk_uid最小的记录delete from code_xz where code in (select code from code_xz group by code having count(code) > 1) and pk_uid not

DELETE FROM py_bond_shenzhen_exchange_opinion_2_1 WHERE id NOT IN (SELECT id FROM (SELECT min(id) AS id FROM py_bond_shenzhen_exchange_opinion_2_1 GROUP BY notice_date, notice_title) temp)

SELECT * FROM EnterpriseDataTools.Enterprise.CompanyMainwhere CompanyNo in (select CompanyNo from EnterpriseDataTools.Enterprise.CompanyMain group by CompanyNo having count(CompanyNo) > 1)and Id not in (select max(Id) from EnterpriseDataTools.Enterpr

验证:mysql 5.6版本 方法一: delete a from table a left join( select (id) from table group by studentName,classId) b on a.id=b.id where b.id is null; 方法二: explain delete from table where id not in (select minid from (select min(id) as minid from table group b

DELETE E FROM t E where E.id> ( SELECT MIN(X.id) FROM t X WHERE X.name = E.name );

用下面的语句就报语法出错: delete from tab_record where recordid not in (select  min(c.recordid) as recordid from  tab_record  c group by (c.dev_Id+c.StartTime+c.EndTime+c.CardNum)); 报错如下:You can't specify target table '表名' for update in FROM clause 找到替代方案,改用下面的,

例如: id           name         value 1               a                 pp 2               a                 pp 3               b                 iii 4               b                 pp 5               b                 pp 6               c           

mysql 查询重复字段,及删除重复记录的方法MySQL, 数据库, 数据库, 字段, 服务器数据库中有个大表,需要查找其中的名字有重复的记录id,以便比较.如果仅仅是查找数据库中name不重复的字段,很容易:SELECT min(`id`),`name` FROM `table` GROUP BY `name`; 但是这样并不能得到说有重复字段的id值.(只得到了最小的一个id值)查询哪些字段是重复的也容易:SELECT `name`,count(`name`) as count FROM `

一:查询及删除重复记录的SQL语句1.查找表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断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 peoplewhere p

查询及删除重复记录的SQL语句 1.查找表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断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

delete from 表 where id not in(select min(id) from 表 group by name ) //删除重复名字的记录 删除之前请用语句 select * from 表 where id in(select min(id) from 表 group by name ) 查看能保留下来的数据. eg.delete from T_bbs_subject where subjectId not in(select min(subjectId) from T_bb

查找所有重复标题的记录:SELECT *FROM t_info aWHERE ((SELECT COUNT(*)FROM t_infoWHERE Title = a.Title) > 1)ORDER BY Title DESC一.查找重复记录1.查找全部重复记录Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)2.过滤重复记录(只显示一条)Select * From HZT Whe

1.所有字段均重复的记录(重复记录保留一条) Select distinct * into #Tmp from tblName Drop table tblName Select * into tblName from #Tmp Drop table #Tmp 设计不周产生的,增加唯一索引可解决 2.所有字段均重复的记录(重复记录保留一条) Select distinct * into #Tmp from tblName Drop table tblName Select * into tblN

查找所有重复标题的记录:SELECT * FROM t_info a WHERE ((SELECT COUNT(*) FROM t_info WHERE Title = a.Title) > 1) ORDER BY Title DESC一.查找重复记录1.查找全部重复记录Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)2.过滤重复记录(只显示一条)Select * From HZ

例如: id name value 1 a pp 2 a pp 3 b iii 4 b pp 5 b pp 6 c pp 7 c pp 8 c iii id是主键 要求得到这样的结果 id name value 1 a pp 3 b iii 4 b pp 6 c pp 8 c iii 方法1 delete YourTable where [id] not in ( select max([id]) from YourTable group by (name + value)) 方法2 delet

感谢孙潇楠前辈的总结,地址http://www.cnblogs.com/sunxiaonan/archive/2009/11/24/1609439.html 例如: id           name         value 1               a                 pp 2               a                 pp 3               b                 iii 4               b      

本文转载自http://www.cnblogs.com/sunxiaonan/archive/2009/11/24/1609439.html 例如: id           name         value 1               a                 pp 2               a                 pp 3               b                 iii 4               b