如何從MySQL中選擇特定的信息

Question

我想從特定的表，行和列中的數字，但似乎無法做到正確。

該表爲tblproducts。該列是qty。我需要選擇id是13。

這是我使用的代碼，但它不返回任何東西：

<?php 
$con=mysqli_connect("localhost","blank","blank","blank"); 
// Check connection 
if (mysqli_connect_errno()) 
    { 
    echo "Failed to connect to MySQL: " . mysqli_connect_error(); 
    } 

$result = mysqli_query($con,"SELECT qty FROM tblproducts"); 

while($row = mysqli_fetch_array($result)) 
    { 
    echo $row['13']; 
    } 

mysqli_close($con); 
?> 

任何幫助，將不勝感激

Answer 1

做這一切在查詢像這樣

SELECT qty FROM tblproducts where id =13

無需迴路

$result = mysqli_query($con,"SELECT qty FROM tblproducts where id =13"); 

$row = mysqli_fetch_assoc($result); 
echo $row['qty']; 

Answer 2

您的sql語法有點不合適，請參閱我的更正。你的回聲row['13']也看起來可疑。您可以使用print_r()打印陣列來查找需要使用的密鑰。這大概是$row['qty']。

<?php 
    $con=mysqli_connect("localhost","blank","blank","blank"); 
    // Check connection 
    if (mysqli_connect_errno()) 
     { 
     echo "Failed to connect to MySQL: " . mysqli_connect_error(); 
     } 

    $result = mysqli_query($con,"SELECT qty FROM tblproducts where id = 13"); 

    while($row = mysqli_fetch_array($result)) 
     { 
     print_r($row); // You can use print_r to have a look at your full array. The index '13' might not be what you where looking for. 
     } 

    mysqli_close($con); 
    ?>