如何限制 Laravel 中特定外键值的行数

Question

我们有一个帖子 table 并且 user_id 是外键例如，我想为这些用户选择帖子

$users=[1,2,13,16,17,19];
$posts = Post::whereIn('user_id', $users)->paginate(10);

但我希望用户 1 和 2 在输出中只有两个帖子，对于其他用户，帖子的数量没有限制。

Note: User 1 and 2 are not always within the $users array, and due to the condition, one or both of them may not be in the array.

你有解决办法吗？

Answer 1

您可以使用 ->take()

$posts = [];
$users=[1,2,13,16,17,19];

foreach($users as $user)
{
    if($user == 1 || $user == 2)
    {
        $posts[] = Post::where('user_id', $user)->take(2)->get();
    }
    else
    {
       $posts[] = Post::where('user_id', $user)->get();
    }
}

在 https://laravel.com/docs/5.7/queries

阅读更多内容

Answer 2

您可以试试这个替代方案：

$posts = [];
$users=[1,2,13,16,17,19];
$userWithJustTwo = [1,2];
$result = array_intersect($users, $userWithJustTwo); 
$posts[] = Post::whereIn('user_id', $result)->orderBy('created_at', 'desc')->take(2)->get();
$array = array_diff($users, userWithJustTwo);
$posts[] = Post::whereIn('user_id', $array)->get();

Answer 3

单次查询是做不到的，我们需要像这样分开取

$users=[1,2,13,16,17,19];
// first take all the post except the two
$posts = Post::whereIn('user_id', $users)->whereNotIn('user_id', [1,2])->get()->toArray();
// then take one user 1 post in desc and limit it by 2
$userOnePost = Post::whereIn('user_id', $users)->where('user_id', 1)->limit(2)->orderBy('post.id', 'desc')->get()->toArray();
// then take one user 2 post in desc and limit it by 2
$userTwoPost = Post::whereIn('user_id', $users)->where('user_id', 2)->limit(2)->orderBy('post.id', 'desc')->get()->toArray();

// merge all the array
$allPost = array_merge(posts,$userOnePost,userTwoPost);

Answer 4

试试这个方法：

$users = User::whereNotIn('id', [1,2])->pluck('id');
$posts = [];

$posts[] = Post::whereIn('user_id', [1,2])->take(2)->get();
$posts[] = Post::whereIn('user_id', $users)->get();

如果你想获得最新的 post 请改用这个：

$posts[] = Post::whereIn('user_id', [1,2])->latest('created_at')->take(2)->get();

Answer 5

你也可以像这样使用参数分组

DB::table('post')
            ->whereIn('user_id', $users)
            ->where(function ($query) {
                $query->whereIn('user_id', [1,2])->limit(2)
                      ->orWhereNotIn('user_id', [1,2]);
            })
            ->get();

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