Computed columns and functions?

Hi all,
I’d like to set up a computed column that uses a function to derive its
data, but can’t seem to find any information on how to do this. My
issue, specifically, is this:

I have a user table and an account activity table, which contains
records of debits and credits to an account, user id as FK. I’d like to
create a computed column within my user table to show the user’s current
balance (sum of credits minus sum of debits). I’ve written a sql query
to compute this when passed in a user id as an argument, but I can’t
figure out how to create the computed column.

Any tips would be much appreciated.

Thanks,
David Benoff

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