mysql - 使用重复的找到的 ID 更新重复的行

Question

我有这样的表:

id     name    description
1      foo      
2      bar
3      foo

我想用重复行的 id 更新描述。像这样的东西:

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

如何在 Mysql 中执行此操作

Answer 1

此查询将返回所有重复的 ID，并以逗号分隔的共享相同名称的 ID 列表:

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

此查询将更新描述:

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working fiddle here .