Обсуждение: [NOVICE] where and how to store calculated data?
I am creating a python CLI app with psql for invoicing.
For sale_invoice_detail table, I have created columns, rate_after_discount and amount_after_discount. I do the appropriate calculations in my python code to set/update values in these columns when rate, qty, discount etc are set/modified.I'm not sure exactly what you are asking but I have two thoughts. * If you want a value to update automatically, the cleanest way to do it it probably to to use a trigger that runs on UPDATE (https://www.postgresql.org/docs/9.6/static/sql-createtrigger.html). * If you are writing your client in python, psql is very much to wrong way to interface with the database. You should be using psycopg2 (http://initd.org/psycopg/docs/). -Ed On 7/5/2017 7:20 AM, Rounak Jain wrote: > I am creating a python CLI app with psql for invoicing. > > For sale_invoice_detail table, I have created columns, > rate_after_discount and amount_after_discount. I do the appropriate > calculations in my python code to set/update values in these columns > when rate, qty, discount etc are set/modified. > > Now, I shall need the sum of the sub-totals (amount_after_discount of > the above table). Should I save this amount in the sale_invoice table > and ensure that the value gets updated when there is any related > change in the sale_invoice_detail table or is there a better way?