Join two queries to form one table - in postgres - sql

Question

I generated a query to pull in unique logins by date, and the average duration of each. What I am now trying to do is add a column representing the logins.
The way I'm pulling in the unique logins is by subtracting the maximum and minimum created date (as this is needed to calculate average duration).
I now have a simple query to calculate all logins (not simply unique logins).
Based on my query - how can I add a column so I will have logins, unique logins, average_duration, and the login_date?
MY QUERY:
SELECT
COUNT(unique_session_ids) as unique_logins
,AVG(
CASE WHEN duration > '0'
THEN duration
END) as average_duration
,login_date
FROM(
SELECT a.session_id as unique_session_ids
,MAX(a.created)-min(a.created) as duration
,MIN(to_char(b.created,'mm-dd')) as login_date
FROM base_identity a
INNER JOIN base_identity b
ON a.session_id = b.session_id
WHERE a.source_system_id = 11
AND a.created >= '2018-12-01'
GROUP BY a.session_id) x
GROUP BY login_date;
WHAT I WANT TO ADD TO THAT:
SELECT COUNT(session_id) as logins
FROM base_identity
GROUP BY to_char(created,'mm-dd')
So, I essentially just want the logins and unique logins represented together.
Thanks!

Answer 1

You can select from multiple tables with the following syntax
SELECT Table1.column_name, Table2.column_name
FROM Table1, Table2
In your case, it would look like
SELECT
COUNT(x.unique_session_ids) as unique_logins
,AVG(CASE WHEN x.duration > '0' THEN x.duration END) as average_duration
,x.login_date
,COUNT(y.session_id)
FROM([...]) x
, base_identity y
GROUP BY x.login_date;