Pairing Send and Receive Data Rows in SQL - sql

Question

Having issues pairing data rows in SQL to identify when an item goes out, but does not return. The send and receive entries are on different rows, and there is a data relationship between the two, so I think this is doable, I'm just stumped as to the solution. The Module and User should tie together the transaction, however there is additionally a "batch" column that could be used to further ensure a unique transaction
Example Table Structure:
MODULE USER EVENTDTTM ACTION Batch
--------------------------------------------------------------------
MODULE1 USERB 2016-01-09 13:00:00 SENT 001
MODULE1 USERB 2016-01-09 13:01:00 RECEIVED 001
MODULE2 USERA 2016-01-09 13:00:00 SENT 001
MODULE2 USERA 2016-01-09 13:01:00 RECEIVED 001
MODULE1 USERA 2016-01-09 13:03:00 SENT 002
MODULE2 USERB 2016-01-09 13:04:00 SENT 002
I've tried a to do a join on the table itself, but I'm only seeing the paired data (with crazy amounts of duplicates)...I cant find the scenarios where an item was sent, but no paired receipt was found.

Answer 1

select *
from
(select * from T where Action = 'SENT') s
left outer join
(select * from T where Action = 'RECEIVED') r
on r.Module and s.Module and r.User = s.User and r.Batch = s.Batch
From the limited amount of sample data it appears that you can uniquely determine a match by having a common module, user and batch. I'm not sure why you came up with duplicates in your queries. The only other issue appears to be using an outer join to keep the "sends" that don't have a "receive" yet.
I think you still wanted everything in the result. If you did only want the unpaired scenarios then add:
where r.Module is null

Answer 2

SELECT
T1.module,
T1.user,
T1.eventdttm,
T1.action,
T1.batch
FROM
My_Table T1
WHERE
T1.action = 'SENT' AND
NOT EXISTS
(
SELECT *
FROM My_Table T2
WHERE
T2.module = T1.module AND
T2.user = T1.user AND
T2.batch = T1.batch AND
T2.action = 'RECEIVED'
)