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如何通过mysql去除重复数据

假设表名为test: select * from (select *, concat(name,code) as __f from test order by date desc) __t group by __f;

假设表名为test: 1 select * from (select *, concat(name,code) as __f from test order by date desc) __t group by __f;

select name, sum(count) as total from table group by name

不建议直接删除,养成良好的习惯(删除更麻烦),以下是将去重后的数据转移到另一张表代码: Insert into 表名(列名)select distinct 列名 from 表名 你可以按照去重的思路,删除重复数据

select userid,username,userlevel from tb where userid not in(select userid from tb group by username,userlevel having count(1)=1)先找出没有重复的userid,然后过滤这些userid,其余的就是有重复的了

MySQL查询重复字段,及删除重复记录的方法 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...

爱应用团队为你解答 http://jingyan.baidu.com/article/73c3ce28ebed94e50343d9fc.html 望采纳

首先先创建一个临时表,然后将author表中无重复的数据拎出来,放进临时表中。 create temporary table 表名 select distinct id,name,password from author 然后将author表中的记录全部删除。 delete from author 最后将临时表中的记录插入author...

delete from temp where id in (select id from (select max(id) as id,count(url) as count from temp group by url having count >1 order by count desc) as tab )

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