MySQL，与同一个表上的字段相关的元组，GROUP BY或SELF JOIN？

Question

我有这些表（简体）：

Appointment(
    INT idAppointment, 
    DATETIME start, 
    DATETIME end) 

AppointmentInvolved(
    INT idAppointment, 
    INT idInvolved) 

Involved(
    INT idInvolved, 
    VARCHAR name, 
    INT type, 
    INT idIncident) 

Incident(
    INT idIncident, 
    VARCHAR description) 

出现了突发事件，可能有几位参与就可以了。每个参与可以有多个任命，并且每个任命可以由多个参与参与。涉及的类型（本例中为principal = 1，secondary = 2）。

鉴于id的约会，我需要知道参与该事件的主体，无论他是否要参加特定的约会。

到目前为止：

SELECT(*) 
FROM Appointments a 
INNER JOIN (AppointmentInvolved ai) ON ai.idAppointment = a.idAppointment, 
INNER JOIN (Involved i) ON i.idInvolved = ai.idInvolved, 
INNER JOIN (Incident in) ON i.idIncident = in.idIncident, 
WHERE a.idAppointment = <WHATEV> 
WHERE in.type=1 

，除非涉及到的主要是要参加这一任命显然是行不通的。 那是一种自我加入吗？我并不需要Incident表，因为可以直接通过idInvolved关联相关人员。

谢谢！

Answer 1

SELECT * 
FROM Involved I 
WHERE I.type=1 
    AND I.idIncident IN (SELECT I2.idIncident 
         FROM AppointmentInvolved AI 
          INNER JOIN Involved I2 ON AI.idInvolved = I2.idInvolved 
          WHERE AI.idAppointment=<WHATEV>)