SQL SELECT聚合来自两个未连接的表

Question

是否可以从两个未连接的表中提取计数？

例如：

SELECT
     (SELECT COUNT(PERSON) FROM PEOPLE),
     COUNT(BUILDINGS)
FROM 
     BUILDINGS

我收到错误说：

  

不是单组小组的功能。

Answer 1

一种方法是在select子句中移动两个计数查询：

select
  (SELECT COUNT(*) FROM PEOPLE) people_cnt,
  (SELECT COUNT(*) FROM BUILDINGS) building_cnt
from dual