Oracle notes

select Z,count(Z) The number of from a
left join b on a.JL=b.bh
where Z is not null
group by Z

select floor((SYSDATE - to_date(birthday,‘yyyy-mm-dd’))/365) AS AGE from temp

select sex ,count(sex) Gender from
(select (case sex
when ‘1’ then ‘ male ’
when ‘2’ then ‘ Woman ’
else ' Unknown ’end)as sex
from temp)t
group by sex