Mysql分组依据（结果的自定义编号）

我有一张桌子

Id Name   Id_collection  Price
1  good1  2              10
2  good2  1              101
3  good3  3              102
4  good4  2              10
5  good5  2              10

我需要按id_集合进行分组，但我需要显示2行（以便能够通过变量或…更改此值，例如：更改为3或4）

或

所以结果一定是

Id Name   Id_collection  Price
1  good1  2              10
4  good4  2              10
2  good2  1              101
3  good3  3              102

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我在考虑程序或循环，但我以前没有，请帮助

要按相邻值分组。在MySQL中。您可以使用变量来分配组。或者，您可以使用此方法来分配组：计算具有

id\u集合

的行数，这些行与具有较小id的每一行不同

您没有指定如何计算其他列，但这里有一个猜测：

select min(id) as id, min(name) as name, id_collection, avg(price) as price
from (select t.*,
             (select count(*)
              from t t2
              where t2.id_collection <> t.id_collection and
                    t2.id < t.id
             ) as grp
      from t
     ) t
group by id_collection, grp;

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我编辑了一点@Gordon_Linoff发布的答案，现在它可以工作了，你只需更改rn@Gordon_Linoff第一个查询工作正常，第二个不正常（显示所有行），对于第一个查询，是否可以显示3个或更多数字而不仅仅是2？@Asylzazazaev。有几个输入错误。@Gordon_Linoff您的第一个示例非常好，但我不知道如何显示3或4个分组“id_collection”计数，现在它显示2个计数，但很快就会更改，第二个示例显示所有数据列表，字段“rn”始终保持为1，请帮助！！！

Id Name   Id_collection  Price
1  good1  2              10
4  good4  2              10
2  good2  1              101
3  good3  3              102

select min(id) as id, min(name) as name, id_collection, avg(price) as price
from (select t.*,
             (select count(*)
              from t t2
              where t2.id_collection <> t.id_collection and
                    t2.id < t.id
             ) as grp
      from t
     ) t
group by id_collection, grp;

select t.*
from (select t.*,
             (@rn := if(@id = id_collection, @rn,
                        if(@id := id_collection, @rn + 1, @rn + 1)
                       )
             ) as rn
      from t cross join
           (select @id = -1, @rn := 0) params
      order by id
     ) t
where rn = 1;

select t.*
from (select t.*,
             (@rn := if(@id = id_collection, @rn + 1,
                        if(@id := id_collection, 1, 0)
                       )
             ) as rn
      from t cross join
           (select @id := -1, @rn := 0) params
      order by id_collection
     ) t
where rn <= 3;