How to sum the amount and merge the offers in a single row?

I have table with discount transactions data as below:

TransactionID	DiscountAmount	DiscountOffer
S011-T012	50	Jun-21
S011-T012	25	ManagerDisc
S011-T025	15	Jul-21

I need to create a table in a way that for a single transaction, Discount amount is summed up and Discount offer is shown side-by-side (maybe with a delimiter between them). For example:

TransactionID	DiscountAmount	DiscountOffer
S011-T012	75	Jun-21 / ManagerDisc
S011-T025	15	Jul-21

I’m able to sum the discount amounts but having a hard time merging the offers.

Can someone provide any tips on how to achieve this?

Answer

You can use GROUP BY, as in:

select
  TransactionID,
  sum(DiscountAmount) as DiscountAmount,
  string_agg(DiscountOffer, ' / ') as DiscountOffer
from t
group by TransactionID