Question

I need to query a table for duplicate deposit records, where two deposits made at one cash terminal, for the same amount, within a certain time window, are considered duplicate records. I’ve started working on a query now, but I would appreciate any advice or suggestions on doing this ‘properly’.

Answer 1

Generally, you’d do a self join to the same table, and put your “duplicate” criteria in the join conditions.

E.g.

SELECT
    *
FROM
    Transactions t1
        inner join
    Transactions t2
        on
            t1.Terminal = t2.Terminal and
            t1.Amount = t2.Amount and
            DATEDIFF(minute,t2.TransactionDate,t1.TransactionDate) between 0 and 10 and
            t1.TransactionID > t2.TransactionID /* prevent matching the same row */