Calculate closest working day in Postgres

Question

I need to schedule some items in a postgres query based on a requested delivery date for an order. So for example, the order has a requested delivery on a Monday (20120319

Answer 1

This gets you previous business day.

SELECT 
    CASE (EXTRACT(ISODOW FROM current_date)::integer) % 7
        WHEN 1 THEN current_date-3
        WHEN 0 THEN current_date-2
        ELSE current_date-1
    END AS previous_business_day