內部聯接SQL查詢

Question

下一條sql語句工作正常。 它同時顯示Patient_id和serv_name，但我嘗試顯示Patient_name而不是Patient_id

SELECT  C1.patient_id, S.serv_name
FROM
    Checkup_Details C
    INNER JOIN Services S ON (C.serv_id=S.serv_id),
    Checkup C1
WHERE
    C1.today = DATE() AND C1.check_id=C.check_id
ORDER BY C.check_id

所以我想如何通過添加此sql語句來做到這一點

INNER JOIN Patient P ON (C1.patient_id=P.patient_id)

但我不知道有多精確。

Answer 1

假設字段Patient_name在Checkup_Details中，則必須輸入

SELECT C1.patient_name ...

取而代之

SELECT C1.patient_id ...

Answer 2

只需添加INNER JOIN子句即可獲取表Patient的列，並通過P.patient_name更改C1.patient_id。

SELECT P.patient_name, S.serv_name
FROM
    Checkup_Details C
    INNER JOIN Services S ON (C.serv_id=S.serv_id),
    INNER JOIN Patient P ON (C1.patient_id=P.patient_id)
    Checkup C1
WHERE
    C1.today = DATE() AND C1.check_id=C.check_id
ORDER BY C.check_id

Answer 3

您不應混合使用隱式和顯式join語法。 一個簡單的規則：請勿在from子句中使用逗號：

SELECT C1.patient_id, S.serv_name
FROM Checkup_Details C  INNER JOIN
     Services S
     ON C.serv_id = S.serv_id INNER JOIN
     Checkup C1
     ON C1.check_id = C.check_id INNER JOIN
     Patient P
     ON C1.patient_id = P.patient_id
WHERE C1.today = DATE()
ORDER BY C.check_id;