There are a number of possible solutions here, but the best way to run a report in this situation is to run it from the Orders table. Create a summary part grouped by the parent customer ID so that they are grouped by the customer, I hope this helps?
Have you looked at the filter option of portals?
or if you have some sort of script that loops through the customers you could use the omit record script step?
Peter is giving a good suggestion, cause in the Orders table you only have the customers with orders :-) Use a relationship to fetch the relevant Customer Info needed.
Happy coding :-)
this one was a big fidgety, thanks for all the suggestions, i had to end up counting the related records on the left side of the relationship and omitting based on the count=0.