Question

我如何选择2个或两者之间？我正在尝试使用此脚本，但它返回错误。

if ($company == "ANY") {
    $query_company = '*';
}
elseif ($company == "AMD") {
    $query_company = 'AMD';
}
elseif ($company == "Intel") {
    $query_company = 'Intel';
}

$card_data =  mysqli_query($con, 
    "SELECT * FROM builds 
    WHERE
        approved = 'yes'
        AND manufacturer = $query_company
        AND build_price BETWEEN $price_min
    AND $price_max
    ");

（我通过GET从网址获取$ company）有什么方法可以使它工作？感谢。

Answer 1

这是你想要的吗？

SELECT *
FROM builds 
WHERE approved = 'yes' and
      (manufacturer = $query_company or $query_company = '*') and
      build_price BETWEEN $price_min AND $price_max;

我只是将此作为您逻辑的示例发布（因此避免SQL注入等问题）。但是，我建议您在应用程序中进行两个不同的查询：

SELECT *
FROM builds 
WHERE approved = 'yes' and
      manufacturer = $query_company and
      build_price BETWEEN $price_min AND $price_max;

和

SELECT *
FROM builds 
WHERE approved = 'yes' and
      build_price BETWEEN $price_min AND $price_max;

这种方法的优点是这些查询可以利用索引。第一个builds(manufacturer, approved, build_price)和第二个builds(approved, build_price)。使用or（或like）的单个查询也无法优化。

编辑：

让我更清楚第二种选择：

if ($company == "ANY") {
    $sql = "SELECT *
            FROM builds 
            WHERE approved = 'yes' and
                  build_price BETWEEN $price_min AND $price_max"
}
else {
    $sql = "SELECT *
            FROM builds 
            WHERE approved = 'yes' and
                  manufacturer LIKE '$query_company' and
                  build_price BETWEEN $price_min AND $price_max"
}

$card_data =  mysqli_query($con, $sql);

这只是一个例子。您可以将$ sql预先分配给大多数查询，然后在if语句中添加附加子句。这种方法有另一个优点。您可以在变量替换后打印$sql以查看它的外观。

也就是说，您应该学习如何切换到参数化查询以防止SQL注入攻击。

Answer 2

一种方法是使用LIKE运算符（注意我已将*替换为%）：

if ($company == "ANY") {
    $query_company = '*';
}
elseif ($company == "AMD") {
    $query_company = 'AMD';
}
elseif ($company == "Intel") {
    $query_company = 'Intel';
}

$card_data =  mysqli_query($con, 
"SELECT * FROM builds 
WHERE approved = 'yes' 
manufacturer LIKE '$query_company'
and build_price BETWEEN $price_min
AND $price_max");

MySQL选择一个，两个或任何

2 个答案: