Question

通常我会这样做以获得2张桌子

<?php 
$select = "SELECT * FROM question ORDER BY id DESC LIMIT 0,20";
$query  = $db->query($select);

while ($fetch = $db->fetch($query)) {
    $uselect = "SELECT * FROM user WHERE id='".intval($fetch['q_user'])."' ";
    $uquery  = $db->query($uselect);
    $ufetch = $db->fetch($uquery);
    ?>    

    Title : <?php echo $fetch['q_title']; ?>
    User : <?php echo $ufetch['u_id']; ?>

    <?php 
} 
?>

有一种简单的方法可以加入这个吗？

Answer 1

嗯，你可以这样做：

SELECT *
FROM question
JOIN user ON question.q_user = user.id
ORDER BY question.id DESC
LIMIT 0, 20

我建议的一件事是明确列出列，因为任何重叠（Question.id和user.id）都是不明确的。只需SELECT question.id, user.id AS uid, ...

即可

Answer 2

SELECT * FROM question JOIN user ON question.q_user = user.id ORDER BY question.id DESC LIMIT 0, 20

有用的链接：http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html

Answer 3

select * from question left join user on user.id = question.q_user order by question.id desc limit 0,20;

Answer 4

SELECT * FROM question 
LEFT JOIN user ON user.id = question.q_user
ORDER BY question.id DESC LIMIT 0,20

Answer 5

此查询应该是正确的：

create table questions
 (
    question_id bigint unsigned auto_increment primary key,
    user_id bigint unsigned not null,
    title varchar(255),
 )engine=innodb;

 create table users
 (
    user_id bigint unsigned auto_increment primary key,
    name varchar(255) not null
 )engine=innodb;

 // your query
 select q.* from questions q
 inner join users u where u.user_id = q.user_id
 order by q.question_id desc

Answer 6

是的，我假设您想要返回提出问题的用户，因为您存储了q_user，那么您需要执行一些SQL：

“SELECT q.q_title，u.u_id FROM question q JOIN user u ON（q.q_user = u.u_id）”

您可以将限制等应用于此查询。

如何加入我的mysql表

6 个答案: