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如何通过mysql去除重复数据

假设:查询一个结果集当中,要求三个字段同时不重复,即当 字段1=A 时,字段2=B 那么其他记录中不再出现字段1=A 并且字段2=B的情况。 select *, count(distinct name) from table group by name 这个 你想去除那些重复 就直接在 distinct 后面 ...

使用DISTINCT关键字即可。 格式如下: SELECT DISTINCT 列名 FROM 表名;

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;

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...

mysql有函数可以取出重复的 distinct select distinct ( name) form aa where name in ('zhang','wang','wang');

方法有很多,这里介绍两种 方法一、如果要保留id的最小值,例如: 数据:执行sql:select count(*) as count ,name,id from ceshi group by name<img 最后要删除的sql为:delete from ceshi where id not in (select count(*) as count ,n...

直接拿1楼的来改吧, delete from zhszty_ebook where id not in( select * from (select max(id) from zhszty_ebook group by url ) as tmp);------------mysql有个特性,对于表进行修改,删除操作,子查询不能和外层的查询的表一样,所以在加...

SELECT* , SUM(num) as '总数'FROMtd_textWHERENAME IN ( SELECT NAME FROM td_text GROUP BY NAME HAVING count(NAME) > 1 )GROUP BY `name`td_text 表数据: 执行sql后

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

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