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
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 .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 ) .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 ) and peopleId not ) .查找表中多余的重复记录(多个字段) select * from vitae a )
1.表结构与数据: CREATE TABLE tablezzl( id int, name ) ); 2.查询出重复的数据: 3.查询出要保留的重复数据: 4.最终的SQL: DELETE FROM tablezzl ) ) a) ) ) b) 5.补充 : 其中这样写mysql中不能如下这样写: DELETE FROM tablezzl ) ) 会报错:You can't specify target table 'tablezzl' for update in FROM clause,不能在
SELECT * FROM tab_init WHERE id IN ( --根据Data分类获取数据最小ID列表 select max(id) from tab_init group by a,b ) 先找出重复数据的 最大的Id ( group by 后面可跟多列, 根据规则找到重复数据), 取出 id 最大或最小的 Id, 然后使用 in查询,就可以得到不重复的数据
--1.建立表:Coursecreate table Course( ID int identity(1,1),--ID Student varchar(20) ,--学生 Sub varchar(20) ,--课程) --2.插入数据INSERT INTO CourseVALUES ('张三','语文'),('李四','语文' ),('王五','语文' ) INSERT INTO CourseVALUES ('张三','语文'),('李四','英语' ),('王五','数学' ) INSERT
参考来自:http://bbs.csdn.net/topics/390737006 1.效果演示 (1)不做处理 (2)合并多列,并对后四列的值做并集处理 2.SQL语句 (1)不做处理 SELECT C .fd_tenantid AS fdTenantId, C .fd_resid AS fdResid, C .fd_res_name AS fdResName, C .fd_service AS fdService, b.fd_get AS fdGET, b.fd_post AS fdPOST
select s.* from ( select *, row_number() over (partition by PersonnelAccount order BY PersonnelID) as group_idx from AUX_SpecialPersonnel ) swhere s.group_idx > 1
方法一: 使用TOP SELECT TOP 1 * FROM user; SELECT TOP 1 * FROM user order by id desc; 方法二: 使用LIMIT SELECT * FROM user LIMIT 1; SELECT * FROM user ORDER BY id ASC LIMIT 1; SELECT * FROM user ORDER BY id DESC LIMIT 1; --------------------- 原文:https://blog.cs
方法一: 使用TOP SELECT TOP 1 * FROM user; SELECT TOP 1 * FROM user order by id desc; 方法二: 使用LIMIT SELECT * FROM user LIMIT 1; SELECT * FROM user ORDER BY id ASC LIMIT 1; SELECT * FROM user ORDER BY id DESC LIMIT 1; 转载至:https://www.cnblogs.com/weimingxin/p
一.条件字段为数值的情况 select * from tb where id=@id; --当前记录 select top 1 * from tb where id>@id order by id; --下一条记录 select top 1 * from tb where id<@id order by id desc --上一条记录 二.以排序的思路出发的一种方案 ;WITH TUsers AS ( SELECT *, ROW_NUMBER() OVER (