I usually use the following statement for pdo MySQL queries
$query = $db->prepare('MySQL statement');
$result = $query->execute(array())
Then use $query->fetch or fetchcolumn (to check Count(*)) to fetch data.
It depends on
PDO::ATTR_ERRMODE, as explained in the Errors and error handling chapter.
If you configure PDO to throw exceptions (
PDO::ERRMODE_EXCEPTION) then no, PDO will automatically throw an exception on error.
In any other case (use the default PDO connection options or explicitly set
PDO::ERRMODE_WARNING) then yes, you need to verify manually the success of each individual operation.
It isn't useful that
PDO::ERRMODE_EXCEPTION is not the default but, you know, PHP has a history of hiding helpful error messages for some misguided user-friendliness.