I'm using SQL Server 2005. I have a payments table with payment id's, user id's, and timestamps. I want to find the most recent payment for each user. This is easy to search and find an answer for. What I also want to know though is if the most recent payment is the user's first payment or not.
I have the following which will number each user's payments:
SELECT
p.payment_id,
p.user_id,
ROW_NUMBER() OVER (PARTITION BY p.user_id ORDER BY p.payment_date) AS paymentNumber
FROM
payment p
I'm not making the mental leap which then lets me then pick the highest paymentNumber per user. If I use the above as a subselect by using MAX(paymentNumber) and then grouping by user_id, I lose the payment_id which I need. But if I also add the payment_id into the group by clause, I'm back to one row per payment. I'm sure I'm overlooking the obvious. Any help?
Try this:
SELECT a.*, CASE WHEN totalPayments>1 THEN 'NO' ELSE 'YES' END IsFirstPayment
FROM(
SELECT p.payment_id,
p.user_id,
ROW_NUMBER() OVER (PARTITION BY p.user_id ORDER BY p.payment_date DESC) AS paymentNumber,
SUM(1) OVER (PARTITION BY p.user_id) AS totalPayments
FROM payment p
) a
WHERE paymentNumber = 1