In addition to eCart, I also developed an Administrative backend using DataAssist to store all of the sales history into a MySQL table.
I have (2) tables that I write to (storing the data) when a transaction occurs...
$WA_table = "orders";
$WA_redirectURL = "";
$WA_indexField = "OrderID";
$WA_fieldNamesStr = "OrderReferenceID|OrderUserID|OrderShipping|OrderTotal|OrderDate|OrderStatus|ppTransID";
$WA_table = "orderdetails";
$WA_redirectURL = "";
$WA_indexField = "DetailOrderID";
$WA_fieldNamesStr = "DetailOrderID|DetailProductID|DetailProductName|DetailProductDesc|DetailQuantity|DetailPrice|DetailOption1";
Having said that, this development took me probably 3 months to finish the 1st time I implemented an eCart web application. I too was really new to all of this and many of the concepts were initially hard for me to grasp.