PHP PDO 行数 - 如何更正？

我有个问题。我们需要知道 SELECT 查询返回的行数。我遇到了各种解决方案，但我不明白哪个是正确的。出于某种原因，在英文 StackOverflow 上，许多人建议简单地而不是SELECT * FROM...做SELECT COUNT(*) FROM.... 如果我有半屏请求怎么办？具有嵌套SELECT'ami、JOIN'ami等魅力？我应该复制它并在任何地方添加 COUNT() 吗？这是歪的，恕我直言。我不想要那个。

还有第二种选择。这样做：

$result = $pdo->query( 'SELECT * FROM `foo_bar`;' );
$count_result = $pdo->query( 'SELECT FOUND_ROWS();' );
$row_count = $count_result->fetchColumn();

然后我们会取回我们需要的东西。但立即的问题是 - 这种方法有哪些限制/错误？陷阱，或不明显的问题。

还有第三种选择。

$result = $pdo->query( 'SELECT * FROM `foo_bar`;' );
$row_count = $result->rowCount();

官方 PDO 文档说 rowCount() 不适用于 SELECT 查询。相反，它写的是不能保证它对所有数据库的正确操作。我的测试表明 MySQL 和 PostgreSQLrowCount()可以正常工作。

毕竟，问题是如何计算 SELECT 查询选择的行数是否正确？

PScount( $result->fetchAll() ) 不提供。即使是悲惨的 100k 记录……你明白的。

请求示例：

$sql="SELECT SQL_CALC_FOUND_ROWS 
    metering.id,
    metering.super_number,
    metering.contract,
    metering.name, 
    metering.city,
    metering.address,
    metering.phone,
    metering.additional_phone,
    metering.responsible,
    metering.name_metering,
    metering.number_card_customer,
    metering.date_contract, 
    metering.date_metering, 
    metering.time_metering,
    metering.status_customer, 
    metering.status, 
    metering.notification,
    metering.date_status, 
    metering.date, 
    metering.creator, 
    metering.type, 
    metering.importance, 
    metering.source_attraction, 
    metering.production, 
    metering.status_metering, 
    metering.delivery_date, 
    metering.delivery_time, 
    metering.production_date,
    user_retail.login AS login_responsible, 
    login_name_metering.login AS login_name_metering, 
    (SELECT COUNT(*) FROM prepay_metering WHERE prepay_metering.id_custom = metering.id) AS prepay,
    (SELECT COUNT(*) FROM manufacture_cost WHERE manufacture_cost.name = metering.id) AS prepay_cost,
    (SELECT COUNT(*) FROM `communication_metering` WHERE `communication_metering`.`id_metering` = `metering`.`id`) AS comment      
    FROM `metering` 
    LEFT JOIN user_retail ON user_retail.id = metering.responsible
    LEFT JOIN user_retail AS login_name_metering ON login_name_metering.id = metering.name_metering
    WHERE
    metering.group_id = '".$_SESSION['group_id']."%' AND
    metering.id LIKE '".$_SESSION['id']."%' AND
    metering.super_number LIKE '".$_SESSION['super_number']."%' AND
    metering.contract LIKE '".$_SESSION['contract']."%' AND
    metering.name LIKE '%".$_SESSION['name']."%' AND
    metering.city LIKE '%".$_SESSION['city']."%' AND
    metering.address LIKE '%".$_SESSION['address']."%' AND
    (metering.phone LIKE '%".$_SESSION['phone']."%' OR metering.additional_phone LIKE '%".$_SESSION['phone']."%') AND
    metering.name_metering LIKE '".$_SESSION['name_metering']."%' AND
    metering.number_card_customer LIKE '".$_SESSION['number_card_customer']."%' AND
    metering.type LIKE '".$_SESSION['type']."%' AND
    metering.responsible LIKE '".$_SESSION['name_responsible']."%'
    ";

这是最初的要求。接下来是这个请求发生了什么的两个屏幕：

$_SESSION['status_customer']=$_POST['status_customer'];
    if (!empty($_SESSION['status_customer'])) $sql.="AND metering.status_customer='".$_SESSION['status_customer']."'";
    $_SESSION['status']=$_POST['status'];
    if (!empty($_SESSION['status'])) $sql.="AND metering.status_customer=2 AND metering.status='".$_SESSION['status']."'";
    $_SESSION['contract_yes']=$_POST['contract_yes'];
    if (!empty($_SESSION['contract_yes'])) $sql.="AND metering.contract!=''";
    $_SESSION['metering_sr']=$_POST['metering'];
    if (!empty($_SESSION['metering_sr'])) $sql.="AND metering.metering='3'";
    //Дата создания
    if (!empty($_SESSION['date1'])) {
        $start_date = substr($_SESSION['date1'],6,4).'-'.substr($_SESSION['date1'],3,2).'-'.substr($_SESSION['date1'],0,2);
        $sql=$sql."AND metering.date >= '".$start_date."'";
    }
    if (!empty($_SESSION['date2'])) {
        $end_date = substr($_SESSION['date2'],6,4).'-'.substr($_SESSION['date2'],3,2).'-'.substr($_SESSION['date2'],0,2);
        $sql=$sql."AND metering.date <= '".$end_date."' ";
    }
    //Дата замера
    if (!empty($_SESSION['date_metering1'])) {
        $start_date = substr($_SESSION['date_metering1'],6,4).'-'.substr($_SESSION['date_metering1'],3,2).'-'.substr($_SESSION['date_metering1'],0,2);
        $sql=$sql."AND metering.date_metering >= '".$start_date."'";
    }
    if (!empty($_SESSION['date_metering2'])) {
        $end_date = substr($_SESSION['date_metering2'],6,4).'-'.substr($_SESSION['date_metering2'],3,2).'-'.substr($_SESSION['date_metering2'],0,2);
        $sql=$sql."AND metering.date_metering <= '".$end_date."' ";
    }
    //Дата контракта
    if (!empty($_SESSION['date_contract1'])) {
        $start_date = substr($_SESSION['date_contract1'],6,4).'-'.substr($_SESSION['date_contract1'],3,2).'-'.substr($_SESSION['date_contract1'],0,2);
        $sql=$sql."AND metering.date_contract >= '".$start_date."'";
    }
    if (!empty($_SESSION['date_contract2'])) {
        $end_date = substr($_SESSION['date_contract2'],6,4).'-'.substr($_SESSION['date_contract2'],3,2).'-'.substr($_SESSION['date_contract2'],0,2);
        $sql=$sql."AND metering.date_contract <= '".$end_date."' ";
    }   
    //Дата доставки
    if (!empty($_SESSION['date_delivery1'])) {
        $start_date = substr($_SESSION['date_delivery1'],6,4).'-'.substr($_SESSION['date_delivery1'],3,2).'-'.substr($_SESSION['date_delivery1'],0,2);
        $sql=$sql."AND metering.delivery_date >= '".$start_date."'";
    }
    if (!empty($_SESSION['date_delivery2'])) {
        $end_date = substr($_SESSION['date_delivery2'],6,4).'-'.substr($_SESSION['date_delivery2'],3,2).'-'.substr($_SESSION['date_delivery2'],0,2);
        $sql=$sql."AND metering.delivery_date <= '".$end_date."' ";
    }       
    //Постраничное отображение
    if (isset($_GET['pag'])) $pag=$_GET['pag'];
    else $pag=0;
    if (empty($_GET['lim'])) $sql .=" LIMIT ".$pag.", 30;";

代码不是我的。有一个任务要转移到 PDO。因此，我不希望看到“歪手”和“谁这样写”的评论，因为它会在错误的地址:) 谢谢