Add running or cumulative total - sql

Question

I have below query which gives me expected results:
SELECT
total_orders,
quantity,
available_store_credits
FROM
(
SELECT
COUNT(orders.id) as total_orders,
date_trunc('year', confirmed_at) as year,
date_trunc('month', confirmed_at) as month,
SUM( quantity ) as quantity,
FROM
orders
INNER JOIN (
SELECT
orders.id,
sum(quantity) as quantity
FROM
orders
INNER JOIN line_items ON line_items.order_id = orders.id
WHERE
orders.deleted_at IS NULL
AND orders.status IN (
'paid', 'packed', 'in_transit', 'delivered'
)
GROUP BY
orders.id
) as order_quantity
ON order_quantity.id = orders.id
GROUP BY month, year) as orders_transactions
FULL OUTER JOIN
(
SELECT
date_trunc('year', created_at) as year,
date_trunc('month', created_at) as month,
SUM( ROUND( ( CASE WHEN amount_in_cents > 0 THEN amount_in_cents end) / 100, 2 )) AS store_credit_given,
SUM( ROUND( amount_in_cents / 100, 2 )) AS available_store_credits
FROM
store_credit_transactions
GROUP BY month, year
) as store_credit_results
ON orders_transactions.month = store_credit_results.month
I want to add one more column beside available_store_credits which will calculate running total of available_store_credits.
These are my trials, but none are working:
Attempt #1
SELECT
total_orders,
quantity,
available_store_credits,
cum_amt
FROM
(
SELECT
COUNT(orders.id) as total_orders,
date_trunc('year', confirmed_at) as year,
date_trunc('month', confirmed_at) as month,
SUM( quantity ) as quantity,
FROM
orders
INNER JOIN (
SELECT
orders.id,
sum(quantity) as quantity
FROM
orders
INNER JOIN line_items ON line_items.order_id = orders.id
WHERE
orders.deleted_at IS NULL
AND orders.status IN (
'paid', 'packed', 'in_transit', 'delivered'
)
GROUP BY
orders.id
) as order_quantity
ON order_quantity.id = orders.id
GROUP BY month, year) as orders_transactions
FULL OUTER JOIN
(
SELECT
date_trunc('year', created_at) as year,
date_trunc('month', created_at) as month,
SUM( ROUND( ( CASE WHEN amount_in_cents > 0 THEN amount_in_cents end) / 100, 2 )) AS store_credit_given,
SUM( ROUND( amount_in_cents / 100, 2 )) AS available_store_credits
SUM( amount_in_cents ) OVER (ORDER BY date_trunc('month', created_at), date_trunc('year', created_at)) AS cum_amt
FROM
store_credit_transactions
GROUP BY month, year
) as store_credit_results
ON orders_transactions.month = store_credit_results.month
Attempt #2
SELECT
total_orders,
quantity,
available_store_credits,
running_tot
FROM
(
SELECT
COUNT(orders.id) as total_orders,
date_trunc('year', confirmed_at) as year,
date_trunc('month', confirmed_at) as month,
FROM
orders
INNER JOIN (
SELECT
orders.id,
sum(quantity) as quantity
FROM
orders
INNER JOIN line_items ON line_items.order_id = orders.id
WHERE
orders.deleted_at IS NULL
AND orders.status IN (
'paid', 'packed', 'in_transit', 'delivered'
)
GROUP BY
orders.id
) as order_quantity
ON order_quantity.id = orders.id
GROUP BY month, year) as orders_transactions
FULL OUTER JOIN
(
SELECT
date_trunc('year', created_at) as year,
date_trunc('month', created_at) as month,
SUM( ROUND( amount_in_cents / 100, 2 )) AS available_store_credits,
SUM (available_store_creds) as running_tot
FROM
store_credit_transactions
INNER JOIN (
SELECT t0.id,
(
SELECT SUM( ROUND( amount_in_cents / 100, 2 )) as running_total
FROM store_credit_transactions as t1
WHERE date_trunc('month', t1.created_at) <= date_trunc('month', t0.created_at)
) AS available_store_creds
FROM store_credit_transactions AS t0
) as results
ON results.id = store_credit_transactions.id
GROUP BY month, year
) as store_credit_results
ON orders_transactions.month = store_credit_results.month

Answer 1

Making some assumptions about the undisclosed table definition and Postgres version (assuming current Postgres 14), this should do it:
SELECT total_orders, quantity, available_store_credits
, sum(available_store_credits) OVER (ORDER BY month) AS cum_amt -- HERE!!
FROM (
SELECT date_trunc('month', confirmed_at) AS month
, count(*) AS total_orders
, sum(quantity) AS quantity
FROM (
SELECT o.id, o.confirmed_at, sum(quantity) AS quantity
FROM orders o
JOIN line_items l ON l.order_id = o.id
WHERE o.deleted_at IS NULL
AND o.status IN ('paid', 'packed', 'in_transit', 'delivered')
GROUP BY 1
) o
GROUP BY 1
) orders_transactions
FULL JOIN (
SELECT date_trunc('month', created_at) AS month
, round(sum(amount_in_cents) FILTER (WHERE amount_in_cents > 0) / 100, 2) AS store_credit_given
, round(sum(amount_in_cents) / 100, 2) AS available_store_credits
FROM store_credit_transactions
GROUP BY 1
) store_credit_results USING (month)
Assuming you want the running sum to show up in every row and order of the date.
First, I simplified and removed some cruft:
date_trunc('year', confirmed_at) as year, was 100 % redundant noise in your query. I removed it.
As was another join to orders. Removed that, too. Assuming orders.id is defined as PK, we can further simplify. See:
PostgreSQL - GROUP BY clause
Use the superior aggregate FILTER. See:
Aggregate columns with additional (distinct) filters
Simplified a couple of other minor bits.