在LEFT JOIN查询中请求随机行

Question

我有2个测验表：“问题”和“答案”。每个问题有4个答案。我想要求50个随机问题。我尝试这个，但它返回的问题少于50个。

（我需要所有50个问题的所有领域和200个答案）。

SELECT Q.*, A.* FROM questions Q 
LEFT JOIN answers A ON Q.pid = A.pid 
WHERE Q.pid >= RAND() * (SELECT MAX(pid) FROM questions) 
AND Q.lid IN $array 
GROUP BY Q.pid 
LIMIT 50 

Answer 1

尝试以下操作：

SELECT y.* 
    FROM 
     (SELECT * 
      FROM questions 
     ORDER 
      BY RAND() LIMIT 2 
    ) x 
    JOIN answers y 
    ON y.question_id = x.question_id 
    ORDER 
    BY x.question_id;