The stored procedure won’t just return the result of the last SELECT. You need to actually return the value: You’re getting the error because Postgres expects the function to return something of type text, but your function doesn’t return anything.
Technically, to repair your statement, you can add LIMIT 1 to the subquery to ensure that at most 1 row is returned. That would remove the error, your code would still be nonsense. Practically, you want to match rows somehow instead of picking an arbitrary row from the remote table store to update every row of your local table customer.Your rudimentary question … Read more