使用PDO获取项目在一个MySQL数据库列中有多少实例的列表

Question

我一直在倾注很多论坛和类似（但不是相同的）我想要完成的问题。我正在更新我的旧mysql查询到PDO。我看到很多人在使用COUNT（*）在PDO中遇到困难，并且有几篇文章用query（）而不是fetch（）或者使用rowCount（）和fetchColumn（）来解释。

但是它们似乎用于检查查询是否返回查询中的任何或零行。也许可以测试一个查询是否有效，或返回单行列出单个查询返回多少行？这不是我想要做的（或者我看错了）。

我想完成的是获得每个唯一项目在给定列中出现次数的列表。我有一个彩弹网站，我想列出每个类别有多少项目。旧的MySQL代码（剪断为了简洁）是这样的：

$query = "SELECT Category, COUNT(*) FROM table WHERE Notes NOT LIKE 'Discontinued' GROUP BY Category"; 
    $result = mysql_query($query); 
    $num_results = $result->num_rows; 

    while($row=mysql_fetch_array($result, MYSQL_NUM)) { 
    echo "$row[0]: $row[1]<br />"; 
    } 

我的结果将是：

航空：312
标记：627个
面具：124
油漆：97
等等等等

所以，现在我试图完成与PDO相同的结果，并尝试了大约我从其他问题拉出了十几个不同的建议 问过了。我通常喜欢自己破解这些问题，这是我第一次不得不扔在毛巾上，实际上在PHP论坛上发布自己的问题。我已经弄得自己很困惑，我不知道哪条路了。

任何从全新角度的指导将非常感激。必须有一种我没有看到或误解的方式。提前致谢！

Answer 1

对于任何人可能正在为这个概念而努力，这是我到目前为止所提出的。我确信有这样做的更干净的方法，但它现在似乎工作正常。由于我也试图将更多面向对象的编码融入到我的一揽子技巧中，因此我最终将解决方案的业务端放入功能中。如果我在重建我的网站时积累了更多的内容，我可能会最终将它们组合到一起，形成一个PDO包装类，或者其他类似的东西。

这里是我的功能：

function fieldCount($field,$condition,$table) 
{ 
//This is just a file that holds the database info and can be whatever name you want 
require('database.ini'); 
try{ 
    $dbh = new PDO("mysql:host=$db_hostname;dbname=$db_database", $db_username, $db_password); 

    //This turns on the error mode so you get warnings returned, if any 
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 

    $stmt = $dbh->prepare("SELECT $field, COUNT(*) AS count FROM $table $condition GROUP BY $field"); 

// I tried to bind my $field variable but for some reason it didn't work so I 
// commented it out below until I can look deeper into it. If anyone sees any 
// glaring errors, please point them out. It looks right to me, but as I said, 
// it's not working. 

// $stmt = $dbh->prepare("SELECT :field, COUNT(*) AS count FROM $table $condition GROUP BY :field"); 
// $stmt->bindParam(':field', $field); 

    $stmt->execute(); 

    $results=$stmt->fetchAll(PDO::FETCH_ASSOC); 
    // Creates an array similar as the following: 
    // $results[0][$field] $results[0]['count'] 
    // $results[1][$field] $results[1]['count'] 
    // $results[2][$field] $results[2]['count'] 
    // with each row as an array of values within a numeric array of all rows 

    $dbh = null; 
} 
catch(PDOException $e) 
{ 
echo $e->getMessage(); 
} 

return $results; 
} 

的database.ini文件看起来如此简单的东西：

<?php 
    //database.ini 

    $db_hostname = 'myHostname'; 
    $db_database = 'databaseNameHere'; 
    $db_username = 'YourUserNameHere'; 
    $db_password = 'YourPasswordHere'; 
?> 

这里是你如何调用该函数：

<?php 
// First you have to "require" your file where the function is located, 
// whatever you name it. 
require('FieldCountFunction.php'); 

// Determine what column in your database you want to get a count of. 
// In my case I want to count how many items there are in each individual 
// category, so the $field is Category here. 
$field = 'Category'; 

// If there is a condition to your query, you would state it here. 
// In my case I wanted to exclude any items in my Inventory table that 
// are marked "Discontinued" in the Notes column of my database. 
$condition = "WHERE Notes NOT LIKE 'Discontinued'"; 

$DB_Table = 'Inventory'; 

// Now you call the function and enter the $field you want to get a count of, 
// any conditions to the query, and the database table name you are querying. 
// The results you collected in the function (it was called $results above), 
// will be dumped into a new array now called "$fieldArray" below. 
$fieldArray = fieldCount($field, $condition, $DB_Table); 

// To get the data out again you can do the following to cycle through the 
// numeric array of rows (that's what the "$i" is for) and from each numbered 
// row you can retrieve the "$field" and "count" that you need. Then display 
// them however you want. I'll just echo them out here. 
$i=0; 
while($i<count($fieldArray)) 
{ 
    echo $fieldArray[$i]["$field"].' : '.$fieldArray[$i]['count'].'<br />'; 
    $totalCount = $totalCount + $fieldArray[$i]['count']; 
    $i++; 
} 
echo $totalCount.' items total'; 
?> 

这将给出类似于以下的结果：

个

配件：638个
标记：432个
面具：146个
包：93
油漆：47个
1356项目总

我希望这可以帮助一个人在那里。如果任何人都可以阐明为什么我的绑定不起作用，我会很感激。如果没有，我相信我会最终弄清楚。