Hi,
I'm assuming that the table you want to pull data from has a date/time stamp field of some sort (I'm going to use the example field LASTUPDDTTM). So you basically want to pull any rows with a last update date/time >= (system date/time the SQR runs - 24 hours)?
So for example if your process runs starts at 2:00 am on 13/02/2009, you'll want to extract any rows in the table created between 2:00 am of 12/02/2009 to 2:00 am of 13/02/2009 (the past 24 hours).
If you have a look at the dates in SQR article, you'll see a number of SQR related date functions. The one you want is dateadd. However the catch is that you want to add -24 hours (or -1 days) which in fact means subtracting 24 hours.
You'll need to store the date 24 hours ago in a variable like this:
let $dtFrom = dateadd(datenow(), 'hour', -24)
Then in your SQL you'll want to filter by rows greater than or equal to this date/time:
...
where LASTUPDDTTM >= $dtFrom
...
Of course, you can change your range from 24 hours to whatever you need.
Hope that helps.