How to Find Users with Multiple Payments on the Same Day Using the Same Account Number and Distinct ZIP Codes?

SQL Query for Identifying Multiple Payments

Database queries are essential for data analysis. This example focuses on the PAYMENT table, containing user IDs, account numbers, ZIP codes, and payment dates. The goal is to pinpoint users who made multiple payments on the same day using the same account number but from different ZIP codes.

We can achieve this using SQL's HAVING clause, which filters grouped results. Here's a query to accomplish this:

SELECT
  user_id,
  account_no,
  date,
  COUNT(*) AS payment_count
FROM
  (SELECT DISTINCT user_id, account_no, zip, date FROM payment) AS distinct_payments
GROUP BY
  user_id,
  account_no,
  date
HAVING
  COUNT(*) > 1;

This query first uses a subquery (distinct_payments) to eliminate duplicate entries based on user_id, account_no, zip, and date. The main query then groups the remaining records by user_id, account_no, and date, counting payments for each group. The HAVING clause ensures only groups with more than one payment (indicating multiple payments from different ZIP codes on the same day) are returned. The payment_count column shows the number of payments for each qualifying user.

This approach effectively identifies suspicious activity where a user might be using multiple locations for transactions on the same day with the same account.

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