Laravel Eloquent 模型：2 个字段，一个 fk 引用另一个表上的 2 个字段

Question

我想使用 Laravel Eloquent 模型和关系来连接我项目中所有表的数据；但是，我在翻译这些关系时遇到了问题。例如，我有两张桌子；第一个是 Books 表，另一个是 Author 表。

Schema::create('books', function (Blueprint $table) {
    $table->increments('id');
    $table->string('code', 20)->unique('ak_books__code')->nullable(false);
    $table->smallInteger('books_type_id');
    $table->float('detection_limit', 10, 0);
    $table->smallInteger('books_classification_id');
    $table->smallInteger('books_number');
    $table->foreign(['books_classification_id', 'books_number'], 'fk_books__classification_scales')
        ->references(['calibration_id', 'number'])->on('classification')
        ->onUpdate('RESTRICT')->onDelete('RESTRICT');
});

Schema::create('classification', function (Blueprint $table) {
    $table->smallInteger('calibration_id');
    $table->smallInteger('number');
    $table->string('name', 50);
    $table->primary(['calibration_id', 'number'], 'pk_classification_scales');
    $table->foreign('calibration_id', 'fk_classification_calibration')->references('id')
        ->on('calibration_parameters')->onUpdate('CASCADE')->onDelete('CASCADE');
});

如何在 Books 表上建立关系以获取 number 和 calibration_id？

Answer 1

和书籍分类一样，我将向您展示一个关于任务-项目之间关系的示例（这个任务的项目是什么）：

任务

/**
 * Run the migrations.
 *
 * @return void
 */
public function up()
{
    Schema::create('tasks', function (Blueprint $table) {
        $table->increments('id');
        $table->string('name');
        $table->text('description');
        $table->string('name');
        $table->integer('project_id')->unsigned();
        $table->timestamp('start_date');
        $table->timestamp('end_date');
        $table->timestamps();

        $table->foreign('project_id')->references('id')->on('projects')->onDelete('cascade')->onUpdate('cascade');
    });
}

/**
 * Reverse the migrations.
 *
 * @return void
 */
public function down()
{
    Schema::dropIfExists('tasks');
}

项目

/**
 * Run the migrations.
 *
 * @return void
 */
public function up()
{
    Schema::create('projects', function (Blueprint $table) {
        $table->increments('id');
        $table->string('name');
        $table->string('description');
        $table->tinyInteger('active')->default(1);
        $table->timestamps();
    });
}

/**
 * Reverse the migrations.
 *
 * @return void
 */
public function down()
{
    Schema::dropIfExists('projects');
}

希望对你有帮助，问候！