Question

我提出了一个问题，但我并不满意，因为我想用Eloquent来做这件事！

以下是查询：

Tournament::leftJoin('category_tournament', 'category_tournament.tournament_id', '=', 'tournament.id')
        ->leftJoin('category_tournament_user', 'category_tournament_user.category_tournament_id', '=', 'category_tournament.id' )
        ->where('category_tournament_user.user_id', '=',$this->id )
        ->select('tournament.*')
        ->distinct()
        ->get();

迁移：

Schema::create('tournaments', function(Blueprint $table) {
    $table->increments('id');
    $table->string('name');
    $table->timestamps();
});

Schema::create('categories', function(Blueprint $table) {
    $table->increments('id');
    $table->string('name');
    $table->timestamps();
});

Schema::create('category_tournament', function(Blueprint $table) {
    $table->increments('id');
    $table->integer('category_id');
    $table->integer('tournament_id');
    $table->timestamps();

    $table->foreign('tournament_id')
            ->references('id')
            ->on('tournament')
            ->onDelete('cascade');

        $table->foreign('category_id')
            ->references('id')
            ->on('category')
            ->onDelete('cascade');
});

Schema::create('category_tournament_user', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('category_tournament_id')->unsigned()->index();
        $table->foreign('category_tournament_id')
            ->references('id')
            ->on('category_tournament')
            ->onDelete('cascade');


        $table->integer('user_id')->unsigned()->index();
        $table->foreign('user_id')
            ->references('id')
            ->on('users')
            ->onDelete('cascade');

        $table->unique(array('category_tournament_id', 'user_id'));

        $table->boolean('confirmed');

        $table->timestamps();
        $table->softDeletes();
        $table->engine = 'InnoDB';


    });

模型

class Tournament extends Model
{
    public function categories()
    {
        return $this->belongsToMany(Category::class);
    }

    public function categoryTournaments()
    {
        return $this->hasMany(CategoryTournament::class);
    }
}

class Category extends Model
{
    public function tournaments()
    {
        return $this->belongsToMany(Tournament::class);
    }

    public function categoryTournament()
    {
        return $this->hasMany(CategoryTournament::class);
    }
}

class CategoryTournament extends Model
{
    protected $table = 'category_tournament';

    public function category()
    {
        return $this->belongsTo(Category::class);
    }

    public function tournament()
    {
        return $this->belongsTo(Tournament::class);
    }

    public function users()
    {
        return $this->belongsToMany(User::class, 'category_tournament_user');
    }
}

class User extends Authenticatable
{
    public function categoryTournaments()
    {
        return $this->belongsToMany(CategoryTournament::class, 'category_tournament_user');
    }
}

查询有效，我只想知道如何用Eloquent做这件事，因为我自己无法做到：（

知道该怎么做???

Answer 1

首先，您必须为迁移添加外键表格+它对于使它们无符号非常有用，因为您可能永远不会有任何负面ID：

$table->integer('tournament_id')->unsigned();
$table->foreign('tournament_id')->references('id')->on('tournaments');

由于您已经拥有模型的关系，因此您应该能够使用eloquent来获取内容。

您可以访问此页面以获取有关Eloquent的更多信息： https://laravel.com/docs/5.0/eloquent

应该是这样的：

$tournaments = Tournament::with('category_tournament')
   ->with('category_tournament_user')    
   ->where('category_tournament_user.user_id', '=',$this->id ) 
   ->distinct()
   ->get();

之后你可以使用$ tournaments的内容：

$tournaments->category_tournament->name;

希望我没有错过任何关键步骤，但我认为应该通过做这些改变来工作。

修改

https://laravel.com/docs/5.1/eloquent-relationships#eager-loading

当访问Eloquent关系作为属性时，关系数据是＆＃34;延迟加载＆＃34;。这意味着在您首次访问该属性之前，实际上不会加载关系数据。然而，Eloquent可以“急切地”加载＆＃34;查询父模型时的关系。急切加载缓解了N + 1查询问题。要说明N + 1查询问题，请考虑与作者相关的Book模型：

在Laravel 5.2中使用eloquent而不是查询

1 个答案: