Question

我有四个表，分别带有各自的“参数”

Movie(name, movie_ID,....)
Ticket(movie_ID, person_ID, ....)
Person(person_DNI, person_ID,....)
Date(person_DNI, Segment)

我需要填写下表

person_ID | person_DNI | movie_ID | Segment

因此，为此，我加入了前两个表（电影和票证），然后是后两个表（日期和人）

SELECT person_ID, movie_ID
FROM `Movie` A JOIN `Ticket` B ON A.movie_ID = B.movie_ID 


SELECT person_DNI, B.person_ID, A.segment
FROM Date A 
LEFT JOIN Person B ON A.person_dni=B.person_DNI

但是现在，如何连接这两个“现在”表？

我的想法是加入Ticket和Person中的person_ID

Answer 1

 SELECT D.person_DNI,  D.Segment, P.person_ID, T.movie_ID
 FROM Date D
 JOIN Person P 
   ON D.person_DNI = P.person_DNI
 JOIN Ticket T
   ON P.person_ID = T.person_ID 

 -- Because you dont use anything from Movie like Movie.name 
 -- you dont really need join Movie to get movie_id
 JOIN Movie M
   ON T.movie_ID = M.movie_ID

Answer 2

由于您尚未详细说明每一列的含义，因此我的答案执行内部联接而无需注意顺序。

最好，您可以在单个查询中联接多个表：

SELECT person_ID, t.person_ID, m.movie_ID, Segment
FROM Person p
JOIN Ticket t ON t.person_ID = p.person_ID
JOIN Movie m ON m.movie_ID = t.movie_ID
JOIN Date d ON d.person_DNI = p.person_DNI

或者（不是很好），您可以通过嵌套查询来查询临时表：

SELECT t1.person_ID, person_DNI, movie_ID, Segment
FROM (
    SELECT person_ID, movie_ID
    FROM `Movie` A JOIN `Ticket` B ON A.movie_ID = B.movie_ID 
) t1 
JOIN (
    SELECT person_DNI, B.person_ID, A.segment
    FROM Date A 
    LEFT JOIN Person B ON A.person_dni = B.person_DNI
) t2
ON t1.person_ID = t2.person_ID

Answer 3

您可以在MySQL中使用自然连接：

SELECT person_ID , person_DNI , movie_ID , Segment
FROM (((Date NATURAL JOIN Person) NATURAL JOIN Ticket ) NATURAL JOIN Movie)

有关更多信息，请查看以下链接：https://www.w3resource.com/mysql/advance-query-in-mysql/mysql-natural-join.php

我希望这会有所帮助。

用MySql连接四个表

3 个答案: