Laravel哪里有查询+与关系

Question

我想获取pwra_dt = $ month && $ year的数据。我能做什么？现在，它显示所有记录！

查询：

$purchaseOrder = PurchaseOrder::whereHas('pwra', function (Builder $query) use ($year, $month) {
    $query->whereYear('pwra_dt', $year)
        ->whereMonth('pwra_dt', $month);

})
->get();

PurchaseOrder（Model）

public function pwra()
{
    return $this->hasMany('App\Models\Pwra', 'purchase_order_uuid', 'purchase_order_uuid');
}

PWRA（模型）

public function purchaseOrder()
{
    return $this->belongsTo('App\Models\PurchaseOrder', 'purchase_order_uuid', 'purchase_order_uuid');
}