mysql查询PHP：我想先将特定项目作为第一个，并可以修改查询要显示的项目数

Question

我有下表。

id  | car_name | owner
-------------------------
1   | Toyota   | Jan
2   | Ford     | Mike
3   | Isuzu    | Andrew
4   | BMW      | Jan
5   | Ferrari  | Steve
6   | Audi     | Jan
7   | Benz     | Kin
8   | Hyundai  | Jan
9   | Kia      | Jan

我想得到所有车主，但如果Jan有5辆或更多车，我可以修改查询并将Jan的前四项列入列表。我不关心我收到剩余物品的订单。我的首要任务是Jan应该是第一个。

id  | car_name | owner
-------------------------
1   | Toyota   | Jan
4   | BMW      | Jan
7   | Benz     | Jan
8   | Hyundai  | Jan
2   | Ford     | Mike
3   | Isuzu    | Andrew
5   | Ferrari  | Steve
6   | Audi     | Bob

Answer 1

我认为你需要枚举值，变量是最简单的方法。然后，额外的连接将为您提供按表中最常用的名称订购的信息：

select t.*
from (select t.*,
             (@rn := if(@n = name, @rn + 1,
                        if(@rn := name, 1, 1)
                       )
             ) as rn
      from t cross join
           (select @n := '', @rn := 0
      order by name
     ) t join
     (select name, count(*) as cnt
      from t
      group by name
     ) tn
     on t.name = tn.name
where rn <= 4
order by cnt desc, name;