How can I Calculate the percentage share of each language in the last 30 days? using Mysql workbench

Question

table

I tried:

select time_spent,language as languages ,
        round(100*count(language)/total,2) as percentage 
from job_data
    cross  join(
                select count(*) as total from Job_data
                ) a
group by 1,2 ;

but i got error

LIMIT 0, 50000 Error Code: 1055. Expression #3 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'a.total' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by 0.000 sec