'Presenting summary information with splitting the value of a column

Is there a way to bring up the following with the table below:

customer_id | loan_date  | loan_amount | loan_paid | status
------------+------------+-------------+-----------+--------
customer1     04/02/2010   5000          3850        active
customer2     04/02/2010   3000          3000        completed
customer3     04/02/2010   6500          4300        defaulted
...

Avg loan, the standard deviation of all the loans, the number of loans, the total amount of defaulted, and the total amount of collected loans per month. (I have data for about 5 years).

I have no idea of where to start.

Solution 1:^[1]

Start like this:

SELECT date_trunc('month', loan_date)
     , avg(loan_amount) AS avg_loan
     , stddev_samp(loan_amount)  AS stddev_samp
     , count(*) AS ct_loans
     , count(*) FILTER (WHERE status = 'defaulted') AS ct_defaulted
     , sum(loan_paid) AS sum_paid
FROM   tbl
GROUP  BY 1
ORDER  BY 1;

Then refine. Details are unclear. Not sure what loan_paid signifies exactly, and what you want to sum exactly. And there are multiple measures under the name of "standard deviation" ...

About aggregate functions.

About date_trunc().

About GROUP BY 1: