如何像主查询一样按子查询分组？

Question

如何像主查询一样应用子查询分组？

这是查询：

select a.clinic_no , 
b.CLINIC_DESC_A , 
a.doctor_no , 
c.STAFF_NATIVE_NAME , 
count(DISCHARGE_FROM_CLINIC) , 
(select count(patient_no) from trng.opd_visits_history WHERE event_date BETWEEN 20240815 and 20240822) as "Total"
from trng.opd_visits_history a , trng.hospital_clinics b  , trng.hospital_staff c 
WHERE event_date BETWEEN 20240815 and 20240822
 and a.CLINIC_NO = b.CLINIC_NO
and a.DOCTOR_NO = c.STAFF_NO 
and b.DOCTOR_NO = c.STAFF_NO
and a.HOSPITAL_NO = 720022
and b.HOSPITAL_NO = 720022
and c.HOSPITAL_NO = 720022  
AND a.DISCHARGE_FROM_CLINIC = 1
group by a.clinic_no , a.doctor_no , b.CLINIC_DESC_A , c.STAFF_NATIVE_NAME

输出如下：

clinic no       doctor no            discharge from clinic    total 
   10               22                         5                1230
   12               15                         4                1230 
   16               19                         7                1230
   20               13                         2                1230 

我需要像这样按子查询进行分组：

select count(patient_no) from trng.opd_visits_history WHERE event_date BETWEEN 20240815 and 20240822 group by clinic_no , doctor_no

当我在子查询中使用 group by 时，它显示错误

ORA-01427 single row subquery returns more than one row 

Answer 1

您正在尝试使用相关子查询，但是 - 您没有在其表与外部表之间应用任何关联。它 must 仅返回一行（值），但是 - 当您将

group by

子句放入其中时 - 它导致返回不止一行，并且出现错误。

类似这样的事情可能会做：

  SELECT a.clinic_no,
         b.CLINIC_DESC_A,
         a.doctor_no,
         c.STAFF_NATIVE_NAME,
         COUNT (DISCHARGE_FROM_CLINIC),
         (SELECT COUNT (patient_no)
            FROM trng.opd_visits_history h
           WHERE     h.clinic_no = a.clinic_no                              --> this
                 AND h.doctor_no = a.doctor_no                              --> this
                 AND event_date BETWEEN 20240815 AND 20240822) AS "Total"
    FROM trng.opd_visits_history a, trng.hospital_clinics b, trng.hospital_staff c
   WHERE     event_date BETWEEN 20240815 AND 20240822
         AND a.CLINIC_NO = b.CLINIC_NO
         AND a.DOCTOR_NO = c.STAFF_NO
         AND b.DOCTOR_NO = c.STAFF_NO
         AND a.HOSPITAL_NO = 720022
         AND b.HOSPITAL_NO = 720022
         AND c.HOSPITAL_NO = 720022
         AND a.DISCHARGE_FROM_CLINIC = 1
GROUP BY a.clinic_no,
         a.doctor_no,
         b.CLINIC_DESC_A,
         c.STAFF_NATIVE_NAME