MySql内连接和＆＃34; OR＆＃34;如果值等于0

Question

所以我有这个内部联接

SELECT IDEvent,events.IDSubject,events.month,events.year
FROM events
    INNER JOIN subjects ON events.IDSubject = subjects.IDSubject
    INNER JOIN classes ON subjects.IDClass = classes.IDClass
    INNER JOIN students ON classes.IDClass = students.IDClass
WHERE events.month=10
    AND events.year=2015
    AND (students.DNI=DNI OR events.IDSubject='0')`

我想要做的是根据用户IDSubject选择所有事件，也许如果IDSubject = 0也有一些事件，我可以得到那些取决于用户的事件，但是不能得到IDSubject = 0的那些，有没有人知道如何正确地做到这一点？

我的数据库模型，如果有人需要看到它

Answer 1

SELECT IDEvent,events.IDSubject,events.month,events.year
FROM events
      INNER JOIN subjects ON events.IDSubject = subjects.IDSubject
      INNER JOIN classes ON subjects.IDClass = classes.IDClass
      INNER JOIN students ON classes.IDClass = students.IDClass
WHERE events.month=10
      AND events.year=2015
      AND students.DNI=DNI
UNION SELECT IDEvent, events.IDSubject ,events.month ,events.year
      FROM events WHERE IDSubject='0'

Answer 2

如果我已经正确理解，你想要所有具有匹配主题的事件，或者让subjectid = 0（我猜不会在主题表中存在）。

SELECT IDEvent
, events.IDSubject
,events.month
,events.year
FROM events
LEFT OUTER JOIN subjects ON events.IDSubject = subjects.IDSubject
INNER JOIN classes ON subjects.IDClass = classes.IDClass
INNER JOIN students ON classes.IDClass = students.IDClass
WHERE (events.IDSubject = 0 OR subjects.IDSubject is not null)
AND events.month = 10
AND events.year = 2015
AND (students.DNI = DNI OR events.IDSubject = 0)