SELECT
sum(TIMESTAMPDIFF( MONTH, `users`.pr_CONTRACT, NOW( ) )) as workduration,
CASE
        WHEN TIMESTAMPDIFF( MONTH, `users`.pr_CONTRACT, NOW( ) )> 6 THEN
        2
        WHEN TIMESTAMPDIFF( MONTH, `users`.pr_CONTRACT, NOW( ) )> 12 THEN
        3
        WHEN TIMESTAMPDIFF( MONTH, `users`.pr_CONTRACT, NOW( ) )> 18 THEN
        4
        WHEN TIMESTAMPDIFF( MONTH, `users`.pr_CONTRACT, NOW( ) )> 24 THEN
        5
        WHEN TIMESTAMPDIFF( MONTH, `users`.pr_CONTRACT, NOW( ) )>= 36 THEN
        6
        END AS workduration_label,
    `users`.pr_CONTRACT
FROM
    `users`
WHERE
    `users`.`id` = '3102'
ORDER BY
    `users`.`id` DESC
    LIMIT 1

work duration | workduration_label | pr_CONTRACT
    22 | 2 | 2017-06-08