PHP-查询的单个结果

Question

I am trying to show the result of a query in my form. I want to see the TOTAL_PRICE of CUSTOMERID=3.

Here is my code:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "database_ps";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $stmt = $conn->prepare("SELECT (COALESCE(a.price, 0) - COALESCE(f.price, 0)) AS total_price FROM tblcustomer c LEFT JOIN (SELECT CustomerID, SUM(Price) as price FROM tblappointment GROUP BY CustomerID ) a ON a.CustomerID = c.CustomerID LEFT JOIN (SELECT CustomerID, SUM(Price) as price FROM tblfinances GROUP BY CustomerID ) f ON f.CustomerID = c.CustomerID where c.CustomerID=3"); 
    $stmt->execute();

    $result = $stmt->setFetchMode(PDO::FETCH_ASSOC); 
}
catch(PDOException $e) {
    echo "Error: " . $e->getMessage();
}
echo $result; 

$conn = null;
?>

my php form is showing as a result 1 instead of 50.

I think it is showing the number of row.

The SQL is working fine. The PHP code is wrong in the end.

Answer 1

Replace your in code:

$result = $stmt->setFetchMode(PDO::FETCH_ASSOC); by $result = $stmt->fetch(PDO::FETCH_ASSOC); and echo $result; by echo $result["total_price"];

setFetchMode sets the default way of fetch ( http://php.net/manual/es/pdostatement.setfetchmode.php ), but does not retrieve data from executed statement (must use fetch)

Your final code will be:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "database_ps";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $stmt = $conn->prepare("SELECT (COALESCE(a.price, 0) - COALESCE(f.price, 0)) AS total_price FROM tblcustomer c LEFT JOIN (SELECT CustomerID, SUM(Price) as price FROM tblappointment GROUP BY CustomerID ) a ON a.CustomerID = c.CustomerID LEFT JOIN (SELECT CustomerID, SUM(Price) as price FROM tblfinances GROUP BY CustomerID ) f ON f.CustomerID = c.CustomerID where c.CustomerID=3"); 
    $stmt->execute();

    $result = $stmt->fetch(PDO::FETCH_ASSOC); 
}
catch(PDOException $e) {
    echo "Error: " . $e->getMessage();
}
echo $fetch["total_price"]; 

$conn = null;
?>