Question

我有表：servers，其中包含我的服务器列表。

---+--------------+---------+----------+
id |  disk_space  | memory  | cpu_core |
---+--------------+---------+----------+
 1 |      100000  |  2048   |   1      |
---+--------------+---------+----------+
 2 |      200000  |  1024   |   2      |
---+--------------+---------+----------+
 3 |      200000  |  2048   |   1      |
---+--------------+---------+----------+
 4 |      100000  |  2048   |   2      |
---+--------------+---------+----------+

如何根据该规格获得最佳服务器（具有多个最大值）？

对于上面的示例，我需要使用id=3获取记录，因为在两个字段（disk_space和memory）中有最大值。

<案例2

---+--------------+---------+----------+
id |  disk_space  | memory  | cpu_core |
---+--------------+---------+----------+
 1 |      100000  |  2048   |   1      |
---+--------------+---------+----------+
 2 |      200000  |  4096   |   4      |
---+--------------+---------+----------+
 3 |      200000  |  2048   |   2      |
---+--------------+---------+----------+
 4 |      400000  |  2048   |   2      |
---+--------------+---------+----------+

这应该返回id = 2

的行

Answer 1

我不知道它是否是正确的语法，但这可行。

SELECT * FROM table ORDER BY disc_space DESC,memory DESC,cpu_core DESC LIMIT 1

Answer 2

我在DB2上工作，所以你可能需要为MYSQL重构这个，但是这会在DB2上做到这一点：

with CTE_MAX_VALUES as (

select max( DISK_SPACE ) as MAX_DISK_SPACE
      ,max( MEMORY )     as MAX_MEMORY
      ,max( CPU_CORE )   as MAX_CPU_CODE
from   SERVERS
)

select     SERVERS.*
from       CTE_MAX_VALUES
cross join SERVERS
order by   case when DISK_SPACE = MAX_DISK_SPACE then 1 else 0 end +
           case when MEMORY     = MAX_MEMORY     then 1 else 0 end +
           case when CPU_CORE   = MAX_CPU_CORE   then 1 else 0 end desc
fetch      first row only

你没有提到如何处理领带。在平局的情况下，如果例如应该在其他列之前选择某个最大列，则可以通过以下方式处理增强的订单：

order by   case when DISK_SPACE = MAX_DISK_SPACE then 1 else 0 end +
           case when MEMORY     = MAX_MEMORY     then 1 else 0 end +
           case when CPU_CORE   = MAX_CPU_CORE   then 1 else 0 end desc
          ,case when CPU_CORE   = MAX_CPU_CORE   then 1 else 0 end desc --tie - 1st choice
          ,case when MEMORY     = MAX_MEMORY     then 1 else 0 end desc --tie - 2nd choice 
          ,case when DISK_SPACE = MAX_DISK_SPACE then 1 else 0 end desc --tie - 3rd choice

如何根据几个标准来决定/查询数据

2 个答案: