Relational Algebra SQL

Question

Hello everyone i was wondering if i could get some help with a problem

Postimi(status)(Post_ID:integer,user_ID:integer,test:string, data:date,time:integer)

I need to fing the Relational Algebra related to Postimi

the question is

List users who posted two or more statuses yesterday while today have not posted any statuses?

if someone could help me. Thank you in Advance

Answer 1

select yd.user_ID
from status yd -- yd for yesterday
where yd.date = current_date() - interval 1 day
and not exists (
  select *
  from status td -- td for today
  where td.user_ID = yd.user_ID
    and td.date = current_date()
)
group by yd.user_ID
having count(*) >= 2

Or

select user_ID
from status
where date >= current_date() - interval 1 day
  and date <= current_date()
group by user_ID
having count(*) >= 2
   and max(date) < current_date()