如何在不使用 Eloquent 的情况下在 Laravel 中使用多表查询

Question

I am using Laravel to create API for my app, later it will be integrated with react front-end. I have two tables, Post & Comment. Post table contains info about posts & comment table contains the comments data about each post. Below is there structure,

• Post Table

post_id (Primary Key) post_title post_description

• Comment Table

comment_id (Primary Key) comment_text post_id (Foreign Key)

I need to take post_id, post_title from post table and total no of comments on each post from comment table & want the json data to be showed like this

        {
            "post_id": 1,
            "post_title": "some title",
            "total comments": "4"

        },

I know how to write sql queries for these but just having issue with showing the data like the above. Below is the code which I am using.

$allPostQuery= DB::select('select * from post');

foreach($allPostQuery as $allPostQuery)

{

$postId= $allPostQuery->post_id;

$totalCommentsQuery= DB::select('select count(comment_id) as totalComments from comment where post_id=:postId',["postId" => $postId ]);

}

return \Response::json([$allPostQuery,$totalCommentsQuery]);

But thats not working. I am confused about the looping of post ids to get total comments for each post. Do I have to do this in front-end using react foreach loop? Anyone can suggest any help. Thanks

Answer 1

As per your question you just need the Post ID, TITLE and Count of the Comments of each posts:

    $query = DB::select('
        SELECT 
            p.post_id, 
            p.title, 
            c.total AS totla_comments
        FROM posts p
        INNER JOIN 
        (
            SELECT post_id, COUNT(post_id) AS total FROM comments WHERE comments.post_id = post_id
            GROUP BY post_id

        ) c
        ON p.post_id = c.post_id
    ');

    echo json_encode($query);

Use json_encode (Laravel has ->json() function) if you want the data return should be in JSON format.

Looking at your approach:

1. First you query the post
2. You loop the post again and query the comments

This will impact your performance speed and should be avoided.