To show information of a table regardless if there's information from another table

[TryingToLearn101]

Hello all,

I am currently using Crystal 2008. What I am trying to accomplish is below:
I want to show all categories that I have from a category table on my report. I also have transactions with different items. Depending on the total weight/product family of these items on the transactions that user will specify, I need to put the total weight to the appropriate category.

For example:
Trans 1001
item ABC product family 1 qty 20
item XYZ product family 2 qty 30
item AAA product family 1 qty 10

Trans 1002
item ABC product family 1 qty 30
item BBB product family 1 qty 10

The end result of the report should be:
Category XXX (representing product family 1 and the total to be quantity is greater than 40) Qty 70
Category YYY (representing product family 1 and the total to be quantity is greater than 10) Qty 30

I know I am oversimplifying the example, but I hope you get the idea of it. What I need is to have the category listed even though I don't the corresponding transactions. I can't do LEFT JOIN because the logic to know what item(s) and how many belong to a category are based on the total of the transactions that user will enter at the prompt. Am I stuck with subreport to do this? I am hoping to be able to avoid using subreport. Any idea is greatly appreciated.

Thank you in advance,
TTL101