Mysqli从两个表中选择 [英] Mysqli select from from two tables

问题描述

我将数据存储在称为"posts"和"comments"的两个不同的表中.现在我正在使用两个mysqli_query.

I have data stored in two different tables called "posts" and "comments". Now i'm using two mysqli_query.

    $q = mysqli_query($db,"SELECT * FROM posts WHERE username='$username'");
    $q = mysqli_query($db,"SELECT * FROM comments WHERE username='$username'");

我可以仅使用一个mysqli_query还是使用3个表吗?

Can I make this with only one mysqli_query or with 3 tables?

推荐答案

您可以简单地连接两个表:

You can simply join both tables:

$q = mysqli_query($db,"SELECT * FROM posts 
LEFT JOIN comments ON comments.username=posts.username 
WHERE comments.username='$username'");

但是，您似乎没有使用ID.我建议您创建ID自动递增字段以建立表之间的关系.如果您不明白我的意思，请尝试按照一个教程进行学习，在我们的一两本书中，您会学到更多，而不仅仅是进入编码尝试做事并试图了解它们的工作原理，甚至都不知道您是否在做.做对了.

However, it looks like you are not using IDs. I suggest you to create ID auto-increment fields to make the relationship between tables. If you don't understand what I mean, try to follow a tutorial and in an our or two you would have learned more, than just by jumping into coding trying to do things and trying to understand how they work without even knowing if you are doing it right.

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