Table not displaying results if parameter not selected

Migrateduser

<p>I'm currently working through BIRT Field Guide 3rd Edition which is great. However I have it set up so a user can choose what is in the report from a list of values (set up parameters) before the report is then run, yet when I run the report without any values specified it doesn't show any results. I do not have the fields as 'required' so they can be left blank.<br><br>
I thought it was due to them being down as 'null value' but when I changed it to just blank,they still show no results in the table. Anyone any idea how you fix this issue?<br><br>
Thanks for any help!<br>
Kate</p>