Question

我在Laravel待了五天，经过几个小时的观看Jeffrey Way后，我决定深入研究构建应用程序以便学习。

我陷入了处理hasManyThrough布局中的表并确定表之间的链接的列。 Eloquent正试图使用名为“id＆＃34;作为它无法找到的主键。在我的表中，我使用命名约定tablename_id，如下所示。在我的类函数中，我指定要使用的列，但它失败并显示错误：

QueryException in Connection.php line 620:
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'cable_installations.id' in 'on clause' (SQL: select `cable_specifications`.*, `cable_installations`.`cable_specifications_id` from `cable_specifications` inner join `cable_installations` on `cable_installations`.`id` = `cable_specifications`.`cable_installations_id` where `cable_installations`.`cable_specifications_id` is null)

我正在尝试检索：

所选cable_installation_method

允许的电缆规格清单

谢谢！

表1：cable_specifications

cable_specifications_id (REPEATS)
other_columns...

表2：cable_installation_methods

cable_installation_methods_id (UNIQUE)
other_columns...

表3：cable_installations（PIVOT）

cable_specifications_id (REPEATS)
cable_installation_methods_id (REPEATS)

我的课程是：

use Illuminate\Database\Eloquent\Model as Eloquent;

 class CableInstallationMethod extends Eloquent {

    protected $table = 'cable_installation_methods';

    protected $fillable = [];

    public function CableInstallation()
    {
        return $this->hasMany('CableInstallation');
    }

    public function CableSpecByInstall()
    {
        return $this->hasManyThrough('App\CableSpecification', 'App\CableInstallation', 'cable_specifications_id', 'cable_installations_id');
    }

}

在我的控制器中，我按下面的说法调用此功能：

public function VoltageDropLoad()
{
    $InstallationMethods = CableInstallationMethod::all();

    $CableSelected =  CableInstallationMethod::where("cable_installation_methods_id", 1)->first();

    $CableTypes = $CableSelected->CableSpecByInstall()distinct()->get()->toJson();

    return view('pages.voltcalc', compact('InstallationMethods', 'CableTypes', 'CableTypes'));
}

Answer 1

根据您的CableInstallationMethod类，您可能错过了为模型定义主键字段的信息：

use Illuminate\Database\Eloquent\Model as Eloquent;

class CableInstallationMethod extends Eloquent {

    protected $table = 'cable_installation_methods';

    /* Need to define $primaryKey column here, normally defaults to 'id' */
    protected $primaryKey = 'cable_installation_methods_id';

    protected $fillable = [];

    public function CableInstallation()
    {
        return $this->hasMany('CableInstallation');
    }

    public function CableSpecByInstall()
    {
       return $this->hasManyThrough('App\CableSpecification', 'App\CableInstallation', 'cable_specifications_id', 'cable_installations_id');
    }

}

使用主键设置，您还可以利用Model :: find（$ id）而不是使用Model：where（...） - ＆gt; first（）

public function VoltageDropLoad()
{
    $InstallationMethods = CableInstallationMethod::all();

    $CableSelected = CableInstallationMethod::find(1);

    $CableTypes = $CableSelected->CableSpecByInstall()->distinct()->get()->toJson();

    return view('pages.voltcalc', compact('InstallationMethods', 'CableTypes', 'CableTypes'));
}

Laravel 5.0找不到很多列的问题

1 个答案: