sql oracle中的count函数不使用group by

Question

如何在sql oracle中使用count函数而不使用group by？

select count(*) as "Total orders",
       nvl(
         (select count (*)
          from   education
          where status='APPROVED'),
         0
       ) as "Number of approved requests"
from   education

Answer 1

使用条件聚合：

select COUNT(*) as "Total orders",
       COUNT(CASE status WHEN 'APPROVED' THEN 1 END)
         as "Number of approved requests"
from   education_expense