Question

We are having issues with an online payment gateway system sometimes duplicating transaction entries within minutes of each other.

We want to create a record of these transactions, so we can analyse and correct them.

Single table, as follows. This shows results for only one card number. We would prefer to return only transactions that occurred on the same day, and preferably within 5 seconds of each other as with the last two rows.

txn_authcode   card_number   cardtype   txn_status   txn_value   entryTimeStamp
-------------------------------------------------------------------------------
1491109220     ....0279      Visa       FAILED       20.00       2011-06-24 19:49:00
1491109219     ....0279      Visa       FAILED       20.00       2012-05-28 22:47:57
1491109218     ....0279      Visa       FAILED       20.00       2012-05-28 22:46:39
1491109217     ....0279      Visa       FAILED       20.00       2012-05-28 22:46:35

So far, I have the following, which gets duplicate records for a given card number, but I am not sure how to granularize this even further in order to get records in the same day and preferably within 5 seconds of each other.

        select * from(
            select  t1.txn_authcode,t1.txn_status,t1.txn_value,t1.entryTimeStamp
                from    transactions t1
                where 1=1
                and exists
                (select null
                 from   transactions t2
                 where  t1.card_number = t2.card_number
                 and t1.entryTimeStamp <> t2.entryTimeStamp
                 and t2.entryTimeStamp >= '2012-05-01'
                 and t2.entryTimeStamp <= '2012-06-01'
                 --*** AND DATEDIFF ( day , t1.entryTimeStamp , t2.entryTimeStamp ) < 1 
    --(datediff above doesn't work as it can return a single record for a given card, 
--but we only want records that have at least one other transaction record on the same 
--day for the same card)

                 )
                 and t1.entryTimeStamp >= '2012-05-01'
                 and t1.entryTimeStamp <= '2012-06-01'
             )x
        order by card_number,entryTimeStamp desc

Could someone give me a hand with this please?

Answer 1

...
AND DATEDIFF ( day , t1.entryTimeStamp , t2.entryTimeStamp ) < 1
AND t1.txn_authcode < t2.txn_authcode
...

Replace your commented out part of query with the above statement and you should get what you need.