Question

我有一个查询（在MySQL中，但这是一个通用的SQL问题），如下所示：

SELECT 'Hits', variable_value 
FROM global_status 
WHERE variable_name = 'QCACHE_HITS'

UNION

SELECT 'Inserts', variable_value 
FROM global_status 
WHERE variable_name = 'QCACHE_INSERTS';

它产生以下结果：

+---------+----------------+
| Hits    | variable_value |
+---------+----------------+
| Hits    | 8330           |
| Inserts | 7075           |
+---------+----------------+

我想要得到的是这两个的比率，它们在同一SQL中。基本上，结果集如下所示：

+---------+----------------+
| Hits    | variable_value |
+---------+----------------+
| Hits    | 8330           |
| Inserts | 7075           |
| H/I     | 1.177
+---------+----------------+

如何编写此SQL？我认为可能需要一个JOIN，但是我不确定如何为SQL中涉及的数学获取两行的 value 。感谢您的指导！

Answer 1

如果您可以将它们作为三个独立的列而不是行接受，则可以执行以下操作：

select max(case when variable_name = 'QCACHE_HITS' then variable_value end) as hits,
       max(case when variable_name = 'QCACHE_INSERTS' then variable_value end) as inserts,
       (max(case when variable_name = 'QCACHE_HITS' then variable_value end) /,
        max(case when variable_name = 'QCACHE_INSERTS' then variable_value end)
       ) as ratio
from global_status ;

取消这一点甚至可能是最简单的：

select h.hits,
       (case when h.hits = 'hits' then hits
             when h.hits = 'inserts' then inserts
             else ratio
        end) 
from (select max(case when variable_name = 'QCACHE_HITS' then variable_value end) as hits,
             max(case when variable_name = 'QCACHE_INSERTS' then variable_value end) as inserts,
             (max(case when variable_name = 'QCACHE_HITS' then variable_value end) /,
              max(case when variable_name = 'QCACHE_INSERTS' then variable_value end)
             ) as ratio
      from global_status
     ) s cross join
     (select 'hits' as hits union all
      select 'inserts' union all
      select 'h/i'
     ) x;

这看起来很复杂，但是基本上只扫描global_status一次（尽管对于一张小桌子来说可能没什么大不了的。）

Answer 2

这将起作用：

SELECT 'Hits', variable_value 
FROM global_status 
WHERE variable_name = 'QCACHE_HITS'

UNION

SELECT 'Inserts', variable_value 
FROM global_status 
WHERE variable_name = 'QCACHE_INSERTS'

UNION

select 'H/I',(SELECT variable_value 
FROM global_status 
WHERE variable_name = 'QCACHE_HITS')/(SELECT variable_value 
FROM global_status 
WHERE variable_name = 'QCACHE_INSERTS') as variable_value
);

Answer 3

由于插入和点击的结果不同，只需合并并按如下所示划分两个单独的子查询并获得o / p

此外，联接不是必需的，因为您不需要额外的列等，而无需额外的行数据

   .... UNION
       Select 'H/I',(SELECT  variable_value 
      FROM global_status 
      WHERE variable_name = 
       'QCACHE_HITS')
       /
    (  SELECT variable_value 
     FROM global_status 
      WHERE variable_name = 
      'QCACHE_INSERTS')

Answer 4

我已经假设您提供的代码可以解决这个问题。

SELECT 'Hits', variable_value 
FROM global_status 
WHERE variable_name = 'QCACHE_HITS'
UNION
SELECT 'Inserts', variable_value 
FROM global_status 
WHERE variable_name = 'QCACHE_INSERTS'
UNION
SELECT 'H/I', (
(SELECT variable_value FROM global_status WHERE variable_name='QCACHE_HITS')
/
(SELECT variable_value FROM global_status WHERE variable_name = 'QCACHE_INSERTS')
) AS 'variable_value';

在不起作用的情况下推荐。祝你好运。

在SQL中如何显示两行的值和这两行的值的比率？

4 个答案: