Note that this function will not always return the actual size of a result set. For example, if you are doing a two-table join along the lines of "SELECT * FROM T1,T2 where T1.x=T2.x" you will get a result of -1. This is due to the 'lazy execution' model in FrontBase whereby result rows are only returned as you request them. If you absolutely have to have the number of rows in advance then you will have to use COUNT(*) first. Most of the time you do not need to know the exact number of rows; it is good enough to know if the size of the result set is non-zero.