You can set up as many datasources on a report as you want .. even to report against different forms in one report as well ,
A datasource allows you to define a 'filter' where you can filter in/out whatever data your require - here you could look at a filter like : text field <> ' ' (ie is not empty)
Detailing this a little more:
First Select the Field (from the Field list) you want to test for emptiness/not answered
Add Line and select <> - not equal to from the Operator list
Add line and enter a space using the literal box, press enter
This will produce the correct syntax to filter out records for a field that is empty.
On reviewing this, the historical use of ' ' was not logical and was a 'workaround'.
<empty> should be used in future.
Any reports that you may already have published will still work if set up using ' ' but if you have need to publish a new version you should change your filter condition to use <empty> (ie the default you are shown when adding 'new line' to the condition)
