php - SQL左连接部分数组为空

Question

我的问题是下面的代码数组的评论和评级区域应该像数据库历史表一样在其中有评论......？

 SELECT users.uid, users.username, history.user_id, history.comment, history.rating
 FROM history
 LEFT JOIN users
 ON users.uid=history.user_id
 WHERE history.book_id="$bid"

它返回：

 Array ( [uid] => 3 [username] => Reign [user_id] => 3 [comment] => [rating] => )

Answer 1

然后你想使用一个INNER JOIN. ALEFT JOIN将返回NULL值。

SELECT users.uid, users.username, history.user_id, history.comment, history.rating
FROM history
INNER JOIN users
ON users.uid=history.user_id
WHERE history.book_id="$bid"