Best way to compare the result of a pdo query

Best way to compare the result of a pdo query

I have the following code that works and does what I want it to but I feel
I'm using more code than is necessary. All I want to do is get the value
in a database cell and check if it is '1' and if so run another query.
$isComplete = $database -> prepare("SELECT completed FROM projects WHERE
id = $project_id");
$isComplete -> execute();
$result = $isComplete -> fetchAll();
$result = count($result);
if($result == 1) { $database -> exec("UPDATE projects SET num_complete =
num_complete - 1 WHERE id = $parent_id"); }