因为数据库没键外键,在关联查询的时候,会碰到查询条数多余数据库实际条数,这因为关联字段在表中有重复值而导致的. 解决方案: 1.数据库脚本删除重复数据,保留最新的一条 2.对关联字段增加唯一约束 例如: 以下表,部门表的部门编号出现了重复. 首先判断是不是重复 select count(*) from department d select count(*) from ( select distinct dept_code from department ) 看以上查出来的数量是不是相同的,不同

create proc insertLog@Title nvarchar(50),@Contents nvarchar(max),@UserId int,@CreateTime datetimeasinsert into Logs values(@Title,@Contents,@UserId,@CreateTime)goexec insertLog 'admin','admin',1,'2018-11-19' 看一下存储过程的定义: 存储过程就是一组为了完成特定功能的SQL 语句集,存储在数据

在网上查找删除重复数据保留id最小的数据,方法如下: DELETE FROM people WHERE peopleName IN ( SELECT peopleName FROM people GROUP BY peopleName HAVING count(peopleName) > ) AND peopleId NOT IN ( SELECT min(peopleId) FROM people GROUP BY peopleName HAVING count(peopleName) >

SELECT * FROM (SELECT addTime FROM motorcade.car_msg_info GROUP BY addTime HAVING COUNT(addTime) > 1) AS b) AND ID NOT IN (SELECT * FROM (SELECT MIN(ID) FROM motorcade.car_msg_info GROUP BY addTime HAVING COUNT(addTime) > 1) AS c) delete from people

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

mysql删除重复数据只保留一条 新建一张测试表: CREATE TABLE `book` ( `id` char(32) NOT NULL DEFAULT '', `name` varchar(100) DEFAULT NULL, `parent_id` char(32) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=gbk; 测试数据: INSERT INTO `book` VALUES ('1', 'n1'

删除重复数据保留name中id最小的记录 delete from order_info where id not in (select id from (select min(id) as id from order_info group by order_number) as b); delete from table where id not in (select min(id) from table group by name having count(name)>1) and  id i

删除重复行 DELETE FROM ecm_member_login_session WHERE (number , client_code) IN ( ) AND update_time NOT IN ( ); 但是报1093错误 :: ) ) Error Code: . You can't specify target table 'ecm_member_login_session' for update in FROM clause 0.046 sec 后来在 嵌套查询语句里面再嵌套一层即

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 `

删除表中重复记录,只保留一条: delete from 表名 where 字段ID in (select * from (select max(字段ID) from 表名 group by 重复的字段 having count(重复的字段) > 1) as b); 实例: 2.当想要为某一个表建立一个唯一索引,由于表中有重复记录而无法进行时,需要删除重复记录. 例表 dept id_no id_name 100 'AAA' 101 'BBB' 102 'CCC' 103 'DDD' 100 'E

目前网上搜索的删除重复记录,大部分都是where子查询,本人感觉看上去不美观,故亲自手写了一个,如下: delete from mst_sku using mst_sku,(  select distinct max(sys_no) as sys_no, sku_code   from mst_sku   group by sku_code   having count(sku_code)>1 ) as t2where mst_sku.sku_code = t2.sku_code and mst

1 查询重复值 ); 2 删除重复值 -- 创建临时表 ) ); -- 把重复数据放进临时表 INSERT Hb_Student_a SELECT id,studentNumber FROM Hb_Student ) ); -- 删除重复数据 DELETE a FROM Hb_Student AS a JOIN Hb_Student_a AS b ON a.id=b.id WHERE a.id=b.id ;

 delete from co_jobinformation cwhere c.name in (select cc.name from co_jobinformation cc group by  cc.name   having count(cc.name) > 1)and rowid not in (select min(rowid) from co_jobinformation e group by e.name having count(e.name )>1)  之前在oracle数

mysql 根据条件删除重复记录 只保留最小id的重复数据 DELETEFROM newsWHERE news_id IN ( SELECT a.news_id FROM ( SELECT news_id FROM news WHERE flag = 1 GROUP BY news_id HAVING count(news_id) > 1 ) a )AND posid NOT IN (SELECT b.posid from ( SELECT min(posid) as posid FROM ne

参考网上的方法,总结了产出重复记录的方法,欢迎交流. 参考:http://www.cnblogs.com/nzbbody/p/4470638.html 方法1:创建一个新表临时储存数据 假设我们有一个存在多个字段的表,表中有部分数据的若干字段重复,此时我们可以使用DISTINCT这个关键字对表数据进行筛选. CREATE [TEMPORARY] TABLE temp LIKE origin_tb; INSERT temp(attr1,attr2,...) SELECT DISTINCT attr

1在日常使用mysql中 前端页面点击次数过多 mysql就会容易产生冗余数据,那这些数据该怎么删除呢 说下思路 查询重复字段id 查询重复字段最小id 删除重复字段ID 保留最小ID 查询重复记录这没的说 SELECT 重复记录字段 from 表 GROUP BY 重复记录字段 HAVING COUNT(*)>1 查询重复字段ID 例如 SELECT id FROM way_bills WHERE source_goods_id in (SELECT source_goods_id from

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

MYSQL里有五百万数据,但大多是重复的,真实的就180万,于是想怎样把这些重复的数据搞出来,在网上找了一圈,好多是用NOT IN这样的代码,这样效率很低,自己琢磨组合了一下,找到一个高效的处理方式,用这个方式,五百万数据,十来分钟就全部去除重复了,请各位参考. 第一步:从500万数据表data_content_152里提取出不重复的字段SFZHM对应的ID字段到TMP3表 create table tmp3 as select min(id) as col1 from data_content

/** 在Mysql下执行: delete from my.stu where id not in( select min(id) id from my.stu group by code) ; 用途是去重复标题,但是却报错! You can't specify target table 'stu' for update in FROM clause 解决办法就是: mysql中不能这么用. (等待mysql升级吧)错误提示就是说,不能先select出同一表中的某些值,再update这个表(在同

如何删除重复数据 业务场景:删除评论表中对同一订单同一商品的重复评论,只保留最早的一条. 查看是否存在对于同一订单同一商品的重复评论. SELECT order_id,product_id,COUNT(*) FROM product_comment GROUP BY order_id,product_id HAVING COUNT(*)>1; 备份product_comment表. CREATE TABLE bak_product_comment_18051801 LIKE product_co