SQL'哪里'子句聚合拉多个字段

Question

我有两张与医院活动有关的表格;第一个用PATIENT_ID和REFERRAL_DATE列出患者转诊，第二个用PATIENT_ID，DISCHARGE_DATE和DISCHARGE_LOCATION列出放电。每位患者可多次转诊和出院

我正在尝试运行一个查询，该查询将为每个推荐人提供后续出院日期和出院地点。

我已经做到这一点了（但是无法弄清楚如何使用聚合函数来为MIN（DISCHARGE_DATE）拉入DISCHARGE_LOCATION）：

SELECT
Referral.PATIENT_ID,
Referral.REFERRAL_DATE,
MIN(Discharge.DISCHARGE_DATE) AS NEXT_DISCHARGE

FROM Referral
LEFT OUTER JOIN Discharge
ON Referral.PATIENT_ID = Discharge.PATIENT_ID
AND Discharge.DISCHARGE_DATE > Referral.REFERRAL_DATE

GROUP BY
Referral.PATIENT_ID,
Referral.REFERRAL_DATE

任何帮助都非常感谢！

表格示例：

Referral:
PATIENT_ID  REFERRAL_DATE
Patient1    10/08/2012
Patient1    05/09/2012
. . .

Discharge:
PATIENT_ID  DISCHARGE_DATE  DISCHARGE_LOCATION
Patient1    01/08/2012      Hospital
Patient1    25/08/2012      Home
Patient1    15/09/2012      Care Home
. . .

我正在寻找的结果是：

PATIENT_ID  REFERRAL_DATE   NEXT_DISCHARGE  DISCHARGE_LOCATION
Patient1    10/08/2012      25/08/2012      Home
Patient1    05/09/2012      15/09/2012      Care Home
. . .

Answer 1

您可以将结果反馈到出院表，以获得理想的结果。

select 
     results.*,
     discharge.DISCHARGE_LOCATION

from 
(
    SELECT
        Referral.PATIENT_ID,
        Referral.REFERRAL_DATE,
        MIN(Discharge.DISCHARGE_DATE) AS NEXT_DISCHARGE    
    FROM Referral
        LEFT OUTER JOIN Discharge
        ON Referral.PATIENT_ID = Discharge.PATIENT_ID
        AND Discharge.DISCHARGE_DATE > Referral.REFERRAL_DATE    
    GROUP BY
        Referral.PATIENT_ID,
        Referral.REFERRAL_DATE
) results
     left join discharge 
          on results.NEXT_DISCHARGE = discharge.discharge_date
          and results.patient_id = discharge.patient_id