Postgresql create view

Question

I have the following columns in Table A which records users fingerprint "transaction" every time they check in or check out from a building.

CREATE TABLE user_transactions(
    id serial PRIMARY KEY,
    staff_id INT4,
    transaction_time TIMESTAMP,
    transaction_type INT4
);

In a single day a user can have many transactions. How can I create a view that with the following stucture?

    staff_id INT4
    transaction_date DATE
    first_transaction TIMESTAMP --first finger scan of the day
    last_transaction TIMESTAMP  --last finger scan of the day
    number_of_transaction INT4  --how many times did the user scan for the day

Answer 1

This one should do the job:

create or replace view xxx as 
select 
    staff_id,
    date_trunc('day', transaction_time) transaction_date, 
    min(transaction_time) first_transaction, 
    max(transaction_time) last_transaction, 
    count(*) 
from user_transactions 
group by staff_id, date_trunc('day', transaction_time);