Hello... I am currently building database for my July and August customers.
Because I am doing a promotion, those that purchased in July will be able to
get a free course in August. I would like to know how do I build it so that
in the "Amount" column, it would search July data and if the customer number
corresponds then it will return the invoice number in July (which is set up
next to the "Amount" column) and if cant find the customer number, then it
should display "100".