CASE WHEN function & date function to change now() > to an assumption date - sql

Question

WITH latest AS (
SELECT
DISTINCT customer_id,
MAX(submitted_on) AS latest_order
FROM orders
GROUP BY 1
),
AA AS (
SELECT
DISTINCT o.customer_id,
latest.latest_order,
now() - INTERVAL '91 days' AS reference_more_than_90D,
now() - INTERVAL '31 days' AS reference_more_than_31D,
now() - INTERVAL '30 days' AS reference_more_than_30D
FROM orders AS o
LEFT JOIN latest
ON o.customer_id = latest.customer_id
GROUP BY 1,2,3,4,5
)
SELECT
DISTINCT o.customer_id,
latest.latest_order,
AA.reference_more_than_30D,
AA.reference_more_than_31D,
AA.reference_more_than_90D,
CASE
WHEN latest.latest_order >= AA.reference_more_than_31D THEN 'r'
WHEN latest.latest_order <= AA.reference_more_than_30D THEN 'a'
ELSE 'l'
END AS status
FROM orders AS o
LEFT JOIN latest
ON o.customer_id = latest.customer_id
LEFT JOIN AA
ON o.customer_id = AA.customer_id
With above this is the output
Seems that my CASE WHEN function isn't working right as 2021-04-29 is an older date than 2022-06-17/2022-06-16 and 2022-04-17 > The status should reflect 'l'
how should i change now() > to an assumption date like 2021-07-01 in this case ? Taking into consideration i only have 2021 & 2020 orders to look at
Thanks

Answer 1

Seems that my CASE WHEN function isn't working right as 2021-04-29 is an older date than 2022-06-17/2022-06-16 and 2022-04-17 > The status should reflect 'l'.
I think you don't need to use those left joins. Please refer to the below script.
WITH latest AS (
SELECT
DISTINCT customer_id,
MAX(submitted_on) AS latest_order
FROM orders
GROUP BY 1
),
AA AS (
SELECT
DISTINCT customer_id,
latest_order,
now() - INTERVAL '91 days' AS reference_more_than_90D,
now() - INTERVAL '31 days' AS reference_more_than_31D,
now() - INTERVAL '30 days' AS reference_more_than_30D
FROM latest
GROUP BY 1,2,3,4,5
)
SELECT
DISTINCT customer_id,
latest_order,
reference_more_than_30D,
reference_more_than_31D,
reference_more_than_90D,
CASE
WHEN latest_order >= reference_more_than_31D THEN 'r'
WHEN latest_order <= reference_more_than_30D THEN 'a'
ELSE 'l' END
AS status
FROM AA
How should I change now() > to an assumption date like 2021-07-01 in this case ? Taking into consideration, I only have 2021 & 2020 orders to look at.
\set variable
hank=> \set name hank
hank=> \set time '2018-02-06 10:09:00'
hank=> select * from tb2 where c2=:'name' and c3>=:'time';
c1 | c2 | c3
----+------+----------------------------
1 | hank | 2018-02-06 10:08:00.78750
How can I set now() to '2021-07-01' ? . I need to make an assumption of the current date to be '2021-07-01'.
CREATE OR REPLACE FUNCTION get_data (v_Date TIMESTAMP WITHOUT TIME ZONE)
RETURNS TABLE (
latest_order TIMESTAMP WITHOUT TIME ZONE,
reference_more_than_30D TIMESTAMP WITHOUT TIME ZONE,
reference_more_than_31D TIMESTAMP WITHOUT TIME ZONE,
reference_more_than_90D TIMESTAMP WITHOUT TIME ZONE
)
AS $$
BEGIN
RETURN QUERY SELECT v_Date,
v_Date - INTERVAL '30 days',
v_Date - INTERVAL '31 days',
v_Date - INTERVAL '91 days';
END;
$$ LANGUAGE plpgsql;
select * from get_data('2021-07-01');

Answer 2

I would suggest avoiding the use of now() as this includes millisecond precision. Instead you probably only need date precision so you could use current_date instead. Plus you really don't need select distinct at all, nor do you need multiple joins etc.
WITH AA
AS (
SELECT customer_id
, CURRENT_DATE - INTERVAL '91 days' AS reference_more_than_90D
, CURRENT_DATE - INTERVAL '31 days' AS reference_more_than_31D
, CURRENT_DATE - INTERVAL '30 days' AS reference_more_than_30D
, MAX(submitted_on) AS latest_order
FROM orders
GROUP BY customer_id
)
SELECT AA.customer_id
, AA.latest_order
, AA.reference_more_than_30D
, AA.reference_more_than_31D
, AA.reference_more_than_90D
, CASE
WHEN AA.latest_order >= AA.reference_more_than_31D
THEN 'r'
WHEN AA.latest_order <= AA.reference_more_than_30D
THEN 'a'
ELSE 'l'
END AS STATUS
FROM AA
If you ned to use a preset date instead of current_date then just use a date literal instead e.g.
SELECT
customer_id
, '2021-07-01'::timestamp - INTERVAL '91 days' AS reference_more_than_90D
, '2021-07-01'::timestamp - INTERVAL '31 days' AS reference_more_than_31D
, '2021-07-01'::timestamp - INTERVAL '30 days' AS reference_more_than_30D
, MAX(submitted_on) AS latest_order
FROM orders
GROUP BY customer_id
)
SELECT AA.customer_id
, AA.latest_order
, AA.reference_more_than_30D
, AA.reference_more_than_31D
, AA.reference_more_than_90D
, CASE
WHEN AA.latest_order >= AA.reference_more_than_31D
THEN 'r'
WHEN AA.latest_order <= AA.reference_more_than_30D
THEN 'a'
ELSE 'l'
END AS STATUS
FROM AA
see this db<>fiddle here