screen/application/common/model/Favourite.php

<?php

namespace app\common\model;

use think\Db;
use think\Model;


class Favourite extends Model
{
    protected $type=[
        'tax'=>'json',
    ];
    protected $autoWriteTimestamp=true;
    protected $updateTime=null;
    protected $createTime='created_at';

    public function goods(){
        return $this->belongsTo(Goods::class,'fav_id');
    }

    public static function delNotExists(){
        self::whereNotExists(GoodsSku::where('id',Db::raw('favourite.goods_sku_id'))->buildSql())->delete();
    }
}