SQL Server 2016

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CREATE TABLE all_transactions
(
	id INT, 
	class VARCHAR(50), 
	date DATETIME, 
	user_id INT
);

INSERT INTO all_transactions
VALUES (1, 'transfer', '2019-04-13 11:02:45', 789), (2, 'transfer', '2019-04-14 05:02:45', 789)
	, (3, 'transfer', '2019-04-15 05:02:45', 711), (4, 'transfer', '2019-04-16 05:02:45', 715);
	
CREATE TABLE helpline_requests
(
	id INT, 
	user_id INT, 
	date DATETIME
);
INSERT INTO helpline_requests
VALUES (1, 789, '2019-04-12 13:02:45'), (2, 789, '2019-04-14 10:59:45'),
	(3, 711, '2019-04-15 11:02:45');
7 rows affected

SELECT * FROM all_transactions;
SELECT * FROM helpline_requests;


id
class
date
user_id


1
transfer
13/04/2019 11:02:45
789

2
transfer
14/04/2019 05:02:45
789

3
transfer
15/04/2019 05:02:45
711

4
transfer
16/04/2019 05:02:45
715




id
user_id
date


1
789
12/04/2019 13:02:45

2
789
14/04/2019 10:59:45

3
711
15/04/2019 11:02:45


;WITH TransactionHelpline24 AS
(
	SELECT at1.user_id AS [User],
		ROW_NUMBER() OVER (PARTITION BY at1.user_id ORDER BY at1.[date]) AS [Occurrence]
	FROM all_transactions at1
	LEFT JOIN helpline_requests ht1 ON at1.user_id = ht1.user_id
	WHERE DATEDIFF(HOUR, ht1.[date], at1.[date]) BETWEEN -24 AND 24
		AND (ht1.[date] >= DATEADD(DAY, -7, GETDATE()) -- Helpline requests for last 7 days only
			OR at1.[date] >= DATEADD(DAY, -7, GETDATE()) -- Transactions for last 7 days only
		)
)


SELECT [User], MAX(Occurrence) AS Occurrences
FROM TransactionHelpline24
GROUP BY [User]
HAVING MAX([Occurrence]) > 1


User
Occurrences


789
3

id	class	date	user_id
1	transfer	13/04/2019 11:02:45	789
2	transfer	14/04/2019 05:02:45	789
3	transfer	15/04/2019 05:02:45	711
4	transfer	16/04/2019 05:02:45	715

id	user_id	date
1	789	12/04/2019 13:02:45
2	789	14/04/2019 10:59:45
3	711	15/04/2019 11:02:45