php - 拉维尔 : MYSQL check if child belongs to top level parent with one query

Question

我有这样的表:

id   |   user   |   parent_id   |   level   |
---------------------------------------------
1    |  parent1 |       0       |     1
2    |  parent2 |       0       |     1
3    |  parent3 |       1       |     2
4    |  child1  |       1       |     2
5    |  child2  |       4       |     3 

来自 child2 我想检查它是否属于 parent1。

一个明显的答案是从每个级别运行查询，从 child2> check parent > check parent > 直到它是 parent1。但这将需要运行很多查询。喜欢:

while ($parent = \DB::table('users')->where('parent_id', $child->parent_id)->first()) {
    if ($checkparent->id == $parent->id) break; // found the checked parent
    else $child = $parent;
}

有什么方法可以只用一个查询来运行它吗？ (注意:会超过2级)

parent1  <-- to here            parent2
/      \
parent3  child1
           \
          child2 <-- from here

Answer 1

我想你正在寻找这个:

Nested has statements may also be constructed using "dot" notation. For example, you may retrieve all posts that have at least one comment and vote:

// Retrieve all posts that have at least one comment with votes...
$posts = Post::has('comments.votes')->get();

有关更多信息，请查看此处 - https://laravel.com/docs/5.3/eloquent-relationships

您需要确保模型中的关系配置正确。