Detect Duplicate Payments

SQLHardSenior levelStripe~15 min

Problem

**[Asked at Stripe]**

A duplicate payment is when the **same customer** uses the **same credit card**
to pay the **same amount** to the **same merchant**, with the transactions
occurring **within 10 minutes of each other**.

Count the total number of duplicate payment events (do not count the original —
only the duplicates).

Tables

Example rows — the live problem includes the full dataset.

transactions

txn_id	merchant_id	card_id	amount	txn_time

Expected output

Your answer should return 1 row with the columns duplicate_count.

Starter code (SQL)

SELECT *
FROM transactions;

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