MySQL：基于列值限制接收到的结果数 合并查询

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我已经对其进行了修改以满足我的特定需求：

SELECt * FROM(    SELECt *, @num := if(@some_id = some_id, @num := @num + 1, 1) as row_num,@some_id := some_id as some_id    FROM example    ORDER BY last_modified DESC) as eWHERe row_num <= 5