条件准备语句 PHP mysqli, reduce答案

【问题标题】：Conditional prepared statements PHP mysqli, reduce条件准备语句 PHP mysqli, reduce
【发布时间】：2017-05-31 12:18:44
【问题描述】：

它有效，但我觉得它不是解决我的问题的最佳方法。我想要我的代码做的是检查 location = 1 并发送所有位置的消息。

function getCurrentMessage($location){
    $conn = Connection::getConnection();

    if($location == 1) {
        $query = "SELECT first_name, last_name, description, title, message ,font_size , effective_date 
                FROM tbl_messages
                JOIN tbl_authors ON tbl_authors.id_author = tbl_messages.id_author 
                JOIN tbl_locations ON tbl_messages.id_location = tbl_locations.id_location
                AND effective_date <= CURDATE()
                ORDER BY effective_date desc
                LIMIT 2;";

        $result = array();

        if ($stmt = $conn->prepare($query)) {
            $stmt->bind_result($first_name, $last_name, $location, $title, $message, $size, $date);
            $stmt->execute();

            while ($stmt->fetch()) {
                $message = new Message($first_name, $last_name, $location, $title, $message, $size, $date);
                array_push($result, $message);
            }
        }
    }
    else{
        $query = "SELECT first_name, last_name, description, title, message ,font_size , effective_date 
                FROM tbl_messages
                JOIN tbl_authors ON tbl_authors.id_author = tbl_messages.id_author 
                JOIN tbl_locations ON tbl_messages.id_location = tbl_locations.id_location
                WHERE tbl_messages.id_location = ?
                AND effective_date <= CURDATE()
                ORDER BY effective_date desc
                LIMIT 2;";

        $result = array();

        if ($stmt = $conn->prepare($query)) {
            $stmt->bind_result($first_name, $last_name, $location, $title, $message, $size, $date);
            $stmt->bind_param('i', $location);
            $stmt->execute();

            while ($stmt->fetch()) {
                $m = new Message($first_name, $last_name, $location, $title, $message, $size, $date);
                array_push($result, $m);
            }
        }
    }

    return $result;
}

也许我可以在 SQL 语句中加入一些逻辑。如果您有任何见解，请提供帮助。

【问题讨论】：

你可以去掉函数开头的位置检查。这将有助于只允许使用一个查询。然后有一个 where 子句，它将从函数中的参数中获取位置，例如 WHERE location=?
code review 是最好的提问地点

标签： php sql database mysqli prepared-statement

【解决方案1】：

只需重构所有不依赖条件的重复部分。

function getCurrentMessage($location){
    $conn = Connection::getConnection();

    if($location == 1) {
        $query = "SELECT first_name, last_name, description, title, message ,font_size , effective_date 
                FROM tbl_messages
                JOIN tbl_authors ON tbl_authors.id_author = tbl_messages.id_author 
                JOIN tbl_locations ON tbl_messages.id_location = tbl_locations.id_location
                AND effective_date <= CURDATE()
                ORDER BY effective_date desc
                LIMIT 2;";

        if (!$stmt = $conn->prepare($query)) {
            return false;
        }

    }
    else{
        $query = "SELECT first_name, last_name, description, title, message ,font_size , effective_date 
                FROM tbl_messages
                JOIN tbl_authors ON tbl_authors.id_author = tbl_messages.id_author 
                JOIN tbl_locations ON tbl_messages.id_location = tbl_locations.id_location
                WHERE tbl_messages.id_location = ?
                AND effective_date <= CURDATE()
                ORDER BY effective_date desc
                LIMIT 2;";

        if (!$stmt = $conn->prepare($query)) {
            return false;
        }
        $stmt->bind_param('i', $location);
    }

    $result = array();

    $stmt->bind_result($first_name, $last_name, $location, $title, $message, $size, $date);
    $stmt->execute();

    while ($stmt->fetch()) {
         $m = new Message($first_name, $last_name, $location, $title, $message, $size, $date);
         array_push($result, $m);
    }

    return $result;
}

您可以走得更远，但这只是一个示例。请注意，如果语句准备失败，该函数如何返回 false。由于您在一个函数内部，这将停止执行该函数并返回 false，因为如果准备失败，则没有进一步的意义。如果你想要一些可以被捕获的东西，你也可以使用异常。

【讨论】：

【解决方案2】：

我现在意识到这个问题应该在代码审查Code review 中发布 , 但是在了解了有关 MYSQL 的更多信息后，我想出了一种清理代码的方法，所以这是我使用控制流函数的答案。
如果您有任何其他想法来进一步清理代码，请告诉我。

$conn = getConnection();
$query = "SELECT first_name, last_name, description, title, message ,font_size , DATE_FORMAT(effective_date,'%h:%i %p %m-%d-%Y')
          FROM tbl_messages
          JOIN tbl_authors ON tbl_authors.id_author = tbl_messages.id_author
          JOIN tbl_locations ON tbl_messages.id_location = tbl_locations.id_location
          WHERE tbl_messages.id_location = IF(? = 1,tbl_messages.id_location,?)
          AND effective_date <= NOW()
          ORDER BY effective_date DESC
          LIMIT 1
          ";

if (!$stmt = $conn->prepare($query)) {
    return false;
}

$stmt->bind_param('ii', $location,$location);

$result = array();

$stmt->bind_result($first_name, $last_name, $location, $title, $message, $size, $date);
$stmt->execute();

while ($stmt->fetch()) {
    $m = new Message($first_name, $last_name, $location, $title, $message, $size, $date);
    array_push($result, $m);
}

return $result;

【讨论】：