Consulta MySql para recuperar el valor del atributo del elemento de xml

$rows = $mysqli->query(<<<EOQ
    SELECT ExtractValue(TestSuiteDefinition,'//test_case/@id') as name
    FROM   TestSuite
    WHERE  TestCaseId=368
EOQ
) or die($mysqli->error);

print_r($rows->fetch_all());

Salida:

Array
(
    [0] => Array
        (
            [0] => 141 142 143 144
        )

)