Question

我是Oracle的初学者，我想知道为什么我不能使用count函数进行求和。这是我查询和尝试的示例：

select job_id, SUM(count(job_id)) as "jobs" 
from employees 
group by job_id

错误：

ORA-00937：不是单组分组功能

我也尝试使用cte，但令我惊讶的是我不能：

with cte1 as (
  select job_id, count(job_id) as "jobs" 
  from employees 
  group by job_id
)
select sum(jobs) from cte1

ORA-00904：“作业”：无效的标识符

Answer 1

您可以嵌套聚合。但是您需要从选择列表中删除要分组的列：

select sum(count(*)) as "jobs" 
from   hr.employees 
group  by job_id;

jobs   
   107

这将计算每个作业的行数。然后总结这些。

与以下相同：

with jobs as ( 
  select count(*) c
  from   hr.employees 
  group  by job_id
)
  select sum ( c ) from jobs;

SUM(C)   
     107

您的CTE失败，因为您引用了“工作”。这使其成为小写标识符，您需要在引号中引用该标识符以进行访问：

with cte1 as(
  select job_id,
         count( job_id ) as "jobs"
  from   hr.employees
  group by job_id
)
  select sum( "jobs" )
  from   cte1;

SUM("JOBS")   
          107

Answer 2

您不需要多余的总和，您已经具有每个job_id的行数：

select job_id, count(job_id) as "jobs" from employees group by job_id

Oracle中的总数

2 个答案: