php - Laravel 查询生成器 "select"奇怪的行为

Question

我对以下代码有疑问:

public function index() {
    $qObj = \DB::table('customers as c')
            ->join('companies_has_customers as chc', 'chc.comhc_cus_id', '=', 'c.cus_id')
            ->join('cuscategory as cc', 'chc.comhc_cca_id', '=', 'cc.cca_id')
            ->join('transactions as t','t.trn_cus_id', '=','c.cus_id')
            ->select('t.trn_id');  

    $qObj->where('comhc_com_id', '=', $this->companyId);


    $res = array(
        'count' => $qObj->count(),
        'items' => $qObj->get()
    );

    //print_r($this->showLastQuery());

    return parent::prepareResponse($res, 200, 'customers');
}

这段代码产生以下 SQL 查询:

select * from `customers` as `c` 
inner join `companies_has_customers` as `chc` on `chc`.`comhc_cus_id` = `c`.`cus_id`     
inner join `cuscategory` as `cc` on `chc`.`comhc_cca_id` = `cc`.`cca_id` 
inner join `transactions` as `t` on `t`.`trn_cus_id` = `c`.`cus_id` 
where comhc_com_id` = 1

问题:

为什么 QueryBuilder 生成 select *... 而不是上面语法中要求的 select t.trn_id...？

Answer 1

改变顺序:

$res = array(
    'items' => $qObj->get(),
    'count' => $qObj->count()
);

它会起作用。

但更好的是，不要两次查询数据库，而是这样做:

$items = $qObj->get();

$res = array(
    'items' => $items,
    'count' => count($items)
);

您的代码的问题在于 count() 方法行为 - 它重置了 columns 属性(使用 select 设置)，仅此而已。