Cómo obtener tiempo de db dependiendo de las condiciones

Utilice timestampdiff función para eso y CASE :

select case 
        when TIMESTAMPDIFF(SECOND, `date`,current_timestamp) <= 60 
        then concat(TIMESTAMPDIFF(SECOND, `date`,current_timestamp), ' seconds')
        when TIMESTAMPDIFF(DAY, `date`,current_timestamp) <= 3 
        and TIMESTAMPDIFF(DAY, `date`,current_timestamp) >= 1 
        ...
       end as time_diff 
from Table_hello
where TIMESTAMPDIFF(DAY, `time`,current_timestamp) >= 3