多个表格没有返回行的内部联接

Question

这个查询有什么问题吗？我都在工作，直到我截断了我的数据库，现在我只有一条记录，当我在phpmyadmin中运行此查询时，它返回0行。

我错过了什么？

SELECT 
Users.id, 
Users.firstname, 
Users.lastname, 
Users.email, 
Users.age, 
Users.phone, 
Universities.Faculty AS university, 
Internship.internship_type AS Internship, 
City.city AS city, 
Interest.interest AS interest, 
Users.filename, 
Users.reg_date 
     FROM Users 
     INNER JOIN City ON Users.city = City.key 
     INNER JOIN Universities ON Users.university = Universities.id 
     INNER JOIN Interes ON Users.interest = Interest.key 
     INNER JOIN Internship ON Users.internship_type = Internship.internship_type 
      ORDER BY `Users`.`id` ASC; 

Answer 1

有可能不会在所有的表中的数据，以便您可以通过使用左连接，并确保至少用户表必须有数据检查：然后逐个改变左加入到内，你不会得到数据会出现问题，但如果其他表的数据是可选的，那么最好使用左连接：

SELECT 
    Users.id, 
    Users.firstname, 
    Users.lastname, 
    Users.email, 
    Users.age, 
    Users.phone, 
    Universities.Faculty AS university, 
    Internship.internship_type AS Internship, 
    City.city AS city, 
    Interest.interest AS interest, 
    Users.filename, 
    Users.reg_date 
FROM Users 
LEFT JOIN City ON Users.city = City.key 
LEFT JOIN Universities ON Users.university = Universities.id 
LEFT JOIN Interes ON Users.interest = Interest.key 
LEFT JOIN Internship ON Users.internship_type = Internship.internship_type 
ORDER BY `Users`.`id` ASC;