内部联接SQL查询

Question

下一条sql语句工作正常。 它同时显示Patient_id和serv_name，但我尝试显示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

所以我想如何通过添加此sql语句来做到这一点

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

但我不知道有多精确。

Answer 1

假设字段Patient_name在Checkup_Details中，则必须输入

SELECT C1.patient_name ...

取而代之

SELECT C1.patient_id ...

Answer 2

只需添加INNER JOIN子句即可获取表Patient的列，并通过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

您不应混合使用隐式和显式join语法。 一个简单的规则：请勿在from子句中使用逗号：

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;