How to combine to values from two records - sql

Question

Hi guys so I have the following code that should look at a event cost, figure out from a transaction table if its been fully paid and from that display the unpaid balance.
Select CASESTUDY_CLIENT.CLEINT_FNAME as First_Name,
casestudy_client.client_sname as Surname,
casestudy_client.client_Phonenumber as Phone_number,
casestudy_event.event_totalcost- casestudy_transaction.transaction_value as Unpaid_balance
from casestudy_client
inner join casestudy_event
on casestudy_client.client_id = casestudy_event.event_clientid
inner join casestudy_transaction
on casestudy_event.event_id = casestudy_transaction.transaction_eventid
where casestudy_event.EVENT_EVENTSTAGE ='complete' and
casestudy_event.event_totalcost > casestudy_transaction.transaction_value;
This works perfectly however if we have a multi part transaction then it fails to pick up the matching event id and assumes its another event.
In my test data I have an event that costs £500, one transaction that has a value of 400 and one transaction with a value of 99. The current output shows the two records one with an unpaid balance of 100 and the other with 401. What I would like to show is just 99
If this is possible in relatively simple way please let me know as I can't figure out how to make it work

Answer 1

You need to add together transactions.
Select CASESTUDY_CLIENT.CLEINT_FNAME as First_Name,
casestudy_client.client_sname as Surname,
casestudy_client.client_Phonenumber as Phone_number,
casestudy_event.event_totalcost- sum(casestudy_transaction.transaction_value) as Unpaid_balance
from casestudy_client
inner join casestudy_event
on casestudy_client.client_id = casestudy_event.event_clientid
inner join casestudy_transaction
on casestudy_event.event_id = casestudy_transaction.transaction_eventid
where casestudy_event.EVENT_EVENTSTAGE ='complete' and
casestudy_event.event_totalcost > casestudy_transaction.transaction_value
GROUP BY CASESTUDY_CLIENT.CLEINT_FNAME, casestudy_client.client_sname, casestudy_client.client_Phonenumber, casestudy_event.event_totalcost
Also, CLEINT_FNAME is probably a typo.

Answer 2

It appears you want to sum the transaction values before subtracting them from the cost.
Select CASESTUDY_CLIENT.CLEINT_FNAME as First_Name,
casestudy_client.client_sname as Surname,
casestudy_client.client_Phonenumber as Phone_number,
casestudy_event.event_totalcost- casestudy_transaction.transaction_value as Unpaid_balance
from casestudy_client
inner join casestudy_event
on casestudy_client.client_id = casestudy_event.event_clientid
inner join (
select casestudy_transaction.transaction_eventid, sum(transaction_value) as transaction_value
from casestudy_transaction
group by casestudy_transaction.transaction_eventid
) as casestudy_transaction
on casestudy_event.event_id = casestudy_transaction.transaction_eventid
where casestudy_event.EVENT_EVENTSTAGE ='complete'
and casestudy_event.event_totalcost> casestudy_transaction.transaction_value ;
I would probably left join the transactions subquery though so you can include the events that haven't been paid for yet, but that just depends on the goal of the query.