Shopping Cart: Am I ready for payment gateway?

[brad]

@max_gb

Database Query

The database query will depend on your setup but in my case I have another server action that inserts products from a shopping cart in data store to the database, and inserts a new record in the table order that contains the user details.

A query is required to find out how much you would like to charge. This wouldn’t be required if you simply only have a single product or service to charge for.

I'm stuck right at the beginning. What exactly am I querying? What do I include in the query? Where am I getting this query from?