Question

I have a problem querying multiple tables in MySQL and am currently at my wits end.

I have unique IDs in each table, and am using an INNER JOIN to combine them; I am quite new to SQL and this may be the wrong method, hence me posting here:

Query:

SELECT res.UserID, res.QuizID, res.QuizResult, u.UserID, u.UserLogin, q.QuizID, q.QuizName, q.QuizFile FROM results res INNER JOIN users u ON (res.UserID = u.UserID)  INNER JOIN quiz q ON (res.QuizID = q.QuizID) 

Table users contains

UserID UserLogin UserPass 

Table quiz contains

QuizID QuizName QuizFile 

Table results contains

UserID QuizID QuizResults 

Can anybody please tell me why I am getting a cartesian product, and how I should go about fixing it?

Answer 1

Try this:

 SELECT res.UserID, res.QuizID, res.QuizResult, u.UserID, u.UserLogin, q.QuizID, q.QuizName, q.QuizFile FROM results as res INNER JOIN users as u ON res.UserID = u.UserID INNER JOIN quiz as q ON res.QuizID = q.QuizID 

A different way to realize something like an INNER JOIN is this:+

 SELECT res.UserID, res.QuizID, res.QuizResult, u.UserID, u.UserLogin, q.QuizID, q.QuizName, q.QuizFile  FROM results as res,users as u ,quiz as q  WHERE res.UserID = u.UserID  AND res.QuizID = q.QuizID