PHP SQL sqlsrv SUM ...分组依据不起作用

<?php
$serverName = "your_server_name";
$connectionOptions = array(
    "Database" => "your_database",
    "Uid" => "your_username",
    "PWD" => "your_password"
);

$conn = sqlsrv_connect($serverName, $connectionOptions);

if ($conn === false) {
    die(print_r(sqlsrv_errors(), true));
}

$sql = "SELECT Category, SUM(SalesAmount) AS TotalSales
        FROM SalesTable
        GROUP BY Category";

$stmt = sqlsrv_query($conn, $sql);

if ($stmt === false) {
    die(print_r(sqlsrv_errors(), true));
}

while ($row = sqlsrv_fetch_array($stmt, SQLSRV_FETCH_ASSOC)) {
    echo "Category: " . $row['Category'] . ", Total Sales: " . $row['TotalSales'] . "<br>";
}

sqlsrv_free_stmt($stmt);
sqlsrv_close($conn);
?>