Java Hibernate JPQL 查询(聚合函数 : count)

Question

在加入期间，我得到下表(示例):

+----------+----------+
| Hostname | Severity |
+----------+----------+
| host1    |   high   |
| host2    |  medium  |
| host1    |   high   |
| host2    |   low    |
| host1    |   low    |
| host2    |   low    |
| host1    |   low    |
| host2    |   high   |
| host1    |   high   |
| host2    |   high   |
+----------+----------+

是否可以创建 JPQL 查询并获得以下结果:

+----------+------+--------+-----+
| Hostname | high | medium | low |
+----------+------+--------+-----+
| host1    |  3   |   0    |  2  |
| host2    |  2   |   1    |  2  |
+----------+------+--------+-----+

我尝试使用 COUNT 和 GROUP BY 但我得到了类似的结果:

host1,high,3
host1,medium,0
host1,low,2

等等...

BR，雷内

Answer 1

标准的 sql 查询看起来像这样 - 我不确定您正在使用的 API 需要付出什么努力，但它是一个非常简单的带有案例逻辑的分组。

select hostname, 
  sum(case when severity = 'high' then 1 else 0 end) as high,
  sum(case when severity = 'medium' then 1 else 0 end) as medium,
  sum(case when severity = 'low' then 1 else 0 end) as low
from
  Table
group by
  hostname
order by
  hostname