Get userwise balance and first transaction date of users in SQL - sql

Question

I have created a Transaction table with columns card_id, amount, created_at. There may be more than 1 row of one user so I want to return the value card_id, sum(amount), first created_at date of all users.
CREATE TABLE Transactions(card_id int, amount money, created_at date)
INSERT INTO Transactions(card_id, amount, created_at)
SELECT 1, 500, '2016-01-01' union all
SELECT 1, 100, '2016-01-01' union all
SELECT 1, 100, '2016-01-01' union all
SELECT 1, 200, '2016-01-02' union all
SELECT 1, 300, '2016-01-03' union all
SELECT 2, 100, '2016-01-04' union all
SELECT 2, 200, '2016-01-05' union all
SELECT 3, 700, '2016-01-06' union all
SELECT 1, 100, '2016-01-07' union all
SELECT 2, 100, '2016-01-07' union all
SELECT 3, 100, '2016-01-07'
I have created function for that but one of my client says I need query not function. Can anyone here suggest what query to use?
CREATE FUNCTION [dbo].[card_id_data]()
RETURNS #t TABLE
(
card_id text,
amount money,
dateOfFirstTransaction date
)
AS
BEGIN
INSERT INTO #t(card_id)
SELECT DISTINCT(card_id) FROM Transactions;
UPDATE #t
SET dateOfFirstTransaction = b.createdat
FROM
(SELECT DISTINCT(card_id) cardid,
MIN(created_at) createdat
FROM Transactions
WHERE amount < 0
GROUP BY card_id) b
WHERE card_id = b.cardid;
UPDATE #t
SET amount = T.AMOUNT
FROM
(SELECT
card_id AS cardid, SUM(MIN(AMOUNT)) AMOUNT, created_at
FROM Transactions
WHERE amount < 0
GROUP BY card_id, created_at) T
WHERE card_id = cardid
AND dateOfFirstTransaction = created_at;
RETURN
END
I want a result as shown in this screenshot:

Answer 1

You can use DENSE_RANK for this. It will number the rows, taking into account tied places (same dates)
SELECT
t.card_id,
SumAmount = SUM(amount),
FirstDate = MIN(t.created_at)
FROM (
SELECT *,
rn = DENSE_RANK() OVER (PARTITION BY t.card_id ORDER BY t.created_at)
FROM dbo.Transactions t
) t
WHERE t.rn = 1
GROUP BY t.card_id;
If the dates are actually dates and times, and you want to sum the whole day, change t.created_at to CAST(t.created_at AS date)

Answer 2

Try this:
/*
CREATE TABLE dbo.Transactions
(
card_id INT,
amount MONEY,
created_at DATE
);
INSERT INTO dbo.Transactions (card_id, amount, created_at)
VALUES (1, 500, '2016-01-01'),
(1, 100, '2016-01-01'),
(1, 100, '2016-01-01'),
(1, 200, '2016-01-02'),
(1, 300, '2016-01-03'),
(2, 100, '2016-01-04'),
(2, 200, '2016-01-05'),
(3, 700, '2016-01-06'),
(1, 100, '2016-01-07'),
(2, 100, '2016-01-07'),
(3, 100, '2016-01-07');
*/
WITH FirstDatePerCard AS
(
SELECT
card_id,
FirstDate = MIN(created_at)
FROM
dbo.Transactions
GROUP BY
card_id
)
SELECT DISTINCT
t.card_id,
SumAmount = SUM(amount) OVER (PARTITION BY t.card_id),
FirstDate = f.FirstDate
FROM
FirstDatePerCard f
INNER JOIN
dbo.Transactions t ON f.card_id = t.card_id AND f.FirstDate = t.created_at
You'll get an output something like this:
card_id SumAmount FirstDate
--------------------------------
1 700.00 2016-01-01
2 100.00 2016-01-04
3 700.00 2016-01-06
Is that what you're looking for??
UPDATE: OK, so you want to sum the amount only for the first_date, for every card_id - is that correct? (wasn't clear from the original question)
Updated my solution accordingly