Question

我试图找出在我的表格中不同的clientId的总数

这是查询

            $stmt = $conn->prepare("SELECT DISTINCT count(clientId) as totalrecords FROM quotes WHERE storeEmail = '". $store['email']. "'");
    $stmt->execute();
    $totalRecords = $stmt->fetch(PDO::FETCH_COLUMN);

            echo 'Total Users Found with Request Quote : ' . $totalRecords . "<br /><br />"; 
            echo 'Press Send button to send notifications to all users <br /><br />'; 

            $query = "SELECT DISTINCT clientId FROM quotes WHERE storeEmail = '". $store['email']. "'";
            $stmt = $conn->prepare($query);
    $stmt->execute();                                
    $clients = $stmt->fetchAll(PDO::FETCH_COLUMN);

第一个查询给出了147的总和，而第二个查询给了我60

第一次查询有什么问题。

Answer 1

COUNT DISTINCT是您正在寻找的：

$query = "SELECT COUNT(DISTINCT clientId) FROM quotes WHERE storeEmail = '". $store['email']. "'";

Answer 2

SELECT DISTINCT count(clientId)将返回您对clientId的计数，无论您是否使用DISTINCT。

但是第二个查询将返回不同的clietIds。

你应该使用

SELECT count(DISTINCT clientId)

Answer 3

两件事：

DISTINCT进入了COUNT。如果使用预准备语句，则应使用参数化查询，如：

$stmt = $conn->prepare("
    SELECT count(DISTINCT clientId) as totalrecords FROM quotes WHERE storeEmail = ?");
$stmt->execute(array($store['email']));

$totalRecords = $stmt->fetch(PDO::FETCH_COLUMN);

echo 'Total Users Found with Request Quote : ' . $totalRecords . "<br /><br />"; 
echo 'Press Send button to send notifications to all users <br /><br />'; 

$query = "SELECT DISTINCT clientId FROM quotes WHERE storeEmail = ?";
        $stmt = $conn->prepare($query);
$stmt->execute(array($store['email']));                                
$clients = $stmt->fetchAll(PDO::FETCH_COLUMN);

从mysql中的表中选择不同的表项

3 个答案: