Laravel查询存在几个

Question

我阅读了有关查询构建器的 Laravel 文档，但我无法理解：

现状：我的用户模型有很多 upperCategories，我的 upperCategory 模型有很多子类别。这就是为什么我可以这样做：auth()->user()->upperCategories()->with('subCategories')->get()->toArray(); 请注意，我使用预先加载来提高性能。这段代码工作正常。它 returns 类似这样的东西：

    [
       "id" => 1,
       "user_id" => 2,
       "category" => "Project",
       "sub_categories" => [
         [
           "id" => 1,
           "upper_category_id" => 1,
           "category" => "myFristProject",
         ],
         [
           "id" => 4,
           "upper_category_id" => 1,
           "category" => "mySecondProject",
         ],
    ]

我想要的：我的子类别模型有很多微类别。我想检查每个 SubCategory 是否存在 microCategory 所以最后我可以创建类似的东西：

       [
           "id" => 1,
           "user_id" => 2,
           "category" => "Project",
           "sub_categories" => [
             [
               "id" => 1,
               "upper_category_id" => 1,
               "category" => "myFristProject",
               "micro_category_exists" => true,
             ],
             [
               "id" => 4,
               "upper_category_id" => 1,
               "category" => "mySecondProject",
               "micro_category_exists" => false,
             ],
        ]

我不想要的是为我拥有的每个子类别发送一个sql查询。我知道我可以使用 exists() 方法解决这样的问题，但是我想在一个查询中完成所有事情。这可能吗？

Answer 1

由于您想向 subCategories 关系添加一个额外的字段，因此您需要向 with 函数添加一个闭包

auth()->user()
    ->upperCategories()
    ->with([
        'subCategories' => function ($query) {
            $query->withCount('microCategories as micro_category_exists');
        }
    ])
    ->get()
    ->toArray();

这个简单的查询将加载 microCategories COUNT，给你这样的东西：

"sub_categories" => [
    [
        "id" => 1,
        "upper_category_id" => 1,
        "category" => "myFristProject",
        "micro_category_exists" => 5,
    ],
    [
        "id" => 4,
        "upper_category_id" => 1,
        "category" => "mySecondProject",
        "micro_category_exists" => 0,
    ],
]

您可以将这些数字用作 truthy/falsy 值（0 可以转换为 php 中的 false）。

如果您确实需要查询中的真值，则需要编写一些自定义逻辑。在 laravel 的最新版本中，withAggregate 函数的存在使这变得非常简单。

auth()->user()
    ->upperCategories()
    ->with([
        'subCategories' => function ($query) {
            $query->withAggregate('microCategories as micro_category_exists', 'count(*) > 0');
        }
    ])
    ->get()
    ->toArray();

"sub_categories" => [
    [
        "id" => 1,
        "upper_category_id" => 1,
        "category" => "myFristProject",
        "micro_category_exists" => true,
    ],
    [
        "id" => 4,
        "upper_category_id" => 1,
        "category" => "mySecondProject",
        "micro_category_exists" => false,
    ],
]

Laravel查询存在几个

Laravel Query Existence of several

performance

query-builder

laravel

laravel-query-builder