Near-Duplicate Transfers

SQL practice question · Hard · Joins · Stripe

transfers has one row per payment (payment_id, payer_id, payee_id, amount, paid_at). A payment is a suspected duplicate when an earlier payment with the same payer_id, payee_id and amount was made at most 5 minutes (300 seconds, inclusive) before it. For each suspected duplicate, return the payment it duplicates: the most recent such earlier payment. Output columns: payment_id, duplicate_of. Order by payment_id ascending.

Table: transfers

Schema of transfers
Column	Type
payment_id	INTEGER
payer_id	INTEGER
payee_id	INTEGER
amount	REAL
paid_at	TIMESTAMP

Schema of transfers

Column

Type

payment_id

INTEGER

payer_id

INTEGER

payee_id

INTEGER

amount

REAL

paid_at

TIMESTAMP

Sample rows of transfers
payment_id	payer_id	payee_id	amount	paid_at
1	10	20	50	2026-01-01 10:00:00
2	10	20	50	2026-01-01 10:02:00
3	10	20	75	2026-01-01 10:03:00
4	11	20	50	2026-01-01 10:01:00

Sample rows of transfers

payment_id

payer_id

payee_id

amount

paid_at

2026-01-01 10:00:00

2026-01-01 10:02:00

2026-01-01 10:03:00

2026-01-01 10:01:00

Expected output on the sample data
payment_id	duplicate_of
2	1

Expected output on the sample data

payment_id

duplicate_of

Solve it in the live editor on this page — run on sample data, then submit against hidden tests.

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