Question

编辑：我已经更改了此问题的标题，因为我实际上没有结果，而不是NULL结果。

我目前正与PDO合作开展我的一个项目，我遇到了一个我似乎无法解决的问题。标准的MySQL查询（在phpMyAdmin中执行）返回我想要的结果，但是当我使用PDO时，它不会产生任何结果。我注意到如果我没有绑定查询的值，那么我想看看我错过了什么......

以下是MySQL查询：

SELECT AVG( demand_value ) 
FROM Demand
WHERE DATE = STR_TO_DATE(  '06 Nov 2013',  '%d %M %Y' ) 
AND TIME
BETWEEN STR_TO_DATE(  '07:00:00',  '%k:%i:%s' ) 
AND STR_TO_DATE(  '10:00:00',  '%k:%i:%s' );

以下是尝试获得相同结果的PHP代码（使用PDO）：

//Assume $date = '06 Nov 2013', $time_from = '07:00:00', $time_to = '10:00:00'
//Those values are parsed in from a custom function
$ave_btwn_times_stmt = 
$connection->get_conn()->prepare("SELECT AVG( demand_value ) 
FROM Demand
WHERE date = STR_TO_DATE(:date, '%d %M %Y')
AND time BETWEEN STR_TO_DATE(:time_from, '%k:%i:%s') 
AND STR_TO_DATE(:time_to, '%k:%i:%s')");

$ave_btwn_times_stmt->bindValue(':date', $date, PDO::PARAM_STR);
$ave_btwn_times_stmt->bindValue(':time_from', $time_from, PDO::PARAM_STR);
$ave_btwn_times_stmt->bindValue(':time_to', $time_to, PDO::PARAM_STR);
$ave_btwn_times_stmt->execute();
$ave_date_times = $ave_btwn_times_stmt->fetchAll();

echo "Average on " . $date . ", between " . $time_from . " and " . $time_to . ": " . $ave_date_times[0][0] . ".";

如果我实施下面的代码，我会得到我想要的结果：

$ave_btwn_times_stmt = 
$connection->get_conn()->prepare("SELECT AVG( demand_value )
FROM Demand 
WHERE date = STR_TO_DATE('$date', '%d %M %Y')
AND time BETWEEN STR_TO_DATE('$from_time', '%k:%i:%s') 
AND STR_TO_DATE('$to_time', '%k:%i:%s')");                                             

$ave_btwn_times_stmt->execute();
$ave_date_times = $ave_btwn_times_stmt->fetchAll();

echo "Average on " . $date . ", between " . $time_from . " and " . $time_to . ": " . $ave_date_times[0][0] . ".";

如果有人能帮我解决这个问题，我将非常感激。

Answer 1

您的MySQL查询引发了此错误

对不起，我担心你不能这样做.SQLSTATE [42S22]：专栏没有发现：1054'where子句'中的未知列'TIME'

我重构了您的查询，删除BETWEEEN并将其替换为2个比较测试。

SELECT AVG( demand_value ) FROM Demand 
       WHERE DATE = STR_TO_DATE( '06 Nov 2013',  '%d %M %Y' ) 
       AND  `time_from` >= STR_TO_DATE( `time_from`,'%k:%i:%s' ) 
       AND  `time_to` >= STR_TO_DATE(`time_to`,'%k:%i:%s' )

使用未命名的占位符，以下代码提供了所需的输出。

$dbh = new PDO("mysql:host=$host;dbname=$database", $username, $password);
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
try {
    $ave_btwn_times_stmt= $dbh->prepare("SELECT AVG( demand_value )
    FROM Demand WHERE DATE = STR_TO_DATE( ?,  '%d %M %Y' )  
    AND  `time_from` >= STR_TO_DATE( ?,'%k:%i:%s' ) 
    AND  `time_to` >= STR_TO_DATE(?,'%k:%i:%s' )");                                             
    // Assign parameters
    $ave_btwn_times_stmt->bindParam(1,$date);
    $ave_btwn_times_stmt->bindParam(2,$time_from);
    $ave_btwn_times_stmt->bindParam(3,$time_to);
    $ave_btwn_times_stmt->execute();
    $ave_date_times = $ave_btwn_times_stmt->fetchAll();
    echo "Average on " . $date . ", between " . $time_from . " and " . $time_to . " = " . $ave_date_times[0][0] . ".";
}
catch(PDOException $e) {
    echo "I'm sorry I'm afraid you can't do that.". $e->getMessage() ;// Remove or modify after testing 
    file_put_contents('PDOErrors.txt',date('[Y-m-d H:i:s]').", mapSelect.php, ". $e->getMessage()."\r\n", FILE_APPEND);  
 }
//Close the connection
$dbh = null;

测试后，您应该删除错误回显或Try / Catch阻止并依赖PHP error handling而不是

MySQL查询产生正确的结果，但使用PDO不会产生任何结果 - 为什么？

1 个答案: