更新具有重复找到的ID的重复行 [英] Update duplicate rows with duplicated found id

问题描述

我有这样的表：

id     name    description
1      foo      
2      bar
3      foo

我想要更新ID与重复行的描述。如下所示：

i want update description with id of duplicated row . something like:

id     name    description
1      foo     duplicate in id (3)
2      bar     
3      foo     duplicate in id (1)  

我如何在Mysql中执行此操作

How can i do this in Mysql

推荐答案

此查询将返回所有重复的ids，并以逗号分隔的ids名称共享相同的名称：

This query will return all duplicated ids with a comma separated list of ids that share the same name:

select
  t1.id,
  group_concat(t2.id)
from
  tablename t1 inner join tablename t2
  on t1.id<>t2.id and t1.name=t2.name
group by
  t1.id

，此查询将更新说明：

update tablename inner join (
  select
    t1.id,
    group_concat(t2.id) dup
  from
    tablename t1 inner join tablename t2
    on t1.id<>t2.id and t1.name=t2.name
  group by
    t1.id
  ) s on tablename.id = s.id
set
  description = concat('duplicate id in (', s.dup, ')')

请看一个< a href =http://sqlfiddle.com/#!9/557f2/1 =nofollow>工作小提琴在这里。

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