Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
740 views
in Technique[技术] by (71.8m points)

mysql - Get most recent row with group by and Laravel

Even though there are multiple questions like this I can't get my query to return the row with the most recent date with a group by.

I have the following table..

| message_id | from | to | created_at | status
----------------------------------------------
|    1       |   1  |  2 | 2017-04-06 |   1
|    2       |   1  |  2 | 2017-04-07 |   0
|    3       |   3  |  4 | 2017-04-06 |   1
|    4       |   3  |  4 | 2017-04-07 |   0
----------------------------------------------

and I'm tryin to get the rows with most recent date.

| message_id | from | to | created_at | status
----------------------------------------------
|    2       |   1  |  2 | 2017-04-07 |   0
|    4       |   3  |  4 | 2017-04-07 |   0

Currently this query returns the rows with the last recent date.

$messages = Message::where('to', Auth::id())
                    ->groupBy('from')
                    ->orderBy('created_at', 'DESC')
                    ->paginate(10);
See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

The problem is that the result set will be first grouped then ordered. You can use nested select to get what you want.

SQL Query:

SELECT t.* FROM (SELECT * FROM messages ORDER BY created_at DESC) t GROUP BY t.from

With Laravel:

$messages = Message::select(DB::raw('t.*'))
            ->from(DB::raw('(SELECT * FROM messages ORDER BY created_at DESC) t'))
            ->groupBy('t.from')
            ->get();

You just need to add your where() clauses.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...