SQL - 存在，加入还是在？

Question

我有3张桌子。 “TERM”，“PERFORMANCE”和“COMPANY”。 TERM表引用了PERFORMANCE.ID，PERFORMANCE具有COMPANY.ID的外键。我如何只获得表演，其中包括：

terms >= now and not null
and only from specific company

╔════════════╦════╦═════════════╦════╦═════════╗
║ TERM       ║    ║ PERFORMANCE ║    ║ COMPANY ║
║ ========== ║ -> ║ =========== ║ -> ║ ======= ║
║ start_date ║    ║ price       ║    ║ name    ║
║ ...        ║    ║ ...         ║    ║ ...     ║
╚════════════╩════╩═════════════╩════╩═════════╝

Answer 1

SELECT *
FROM Perfomance a 
INNER JOIN Term b on a.XX = b.XX
INNER JOIN Company c on a.XX = c.XX
where
C.Name = ' '

Answer 2

试试这个：

SELECT T.start_date, P.price, C.name  
FROM PERFORMANCE P JOIN
     COMPANY C ON P.COMPANY.ID=C.ID JOIN
     TERM T ON T.PERFORMANCE.ID=P.ID

尝试详细了解JOIN s。