Yes, most of the fields are arriving in Perl as undef, there are a few that arrive as empty but I'm converting these into undef when found. The use of NULL's is by design. The data I'm collecting my not be complete and as I don't control the raw data there is not much I can do about this. The information (as you may have guessed) is weather data and I'll be calculating average and various other stats from it. I have to use NULL to differentiate between actual data and missing data - I can't use zero for example because it's a real value 0 degrees Celsius is a valid temperature. It's even worse with other parameters as prior to the solution to my Barometric Pressure was being populated with 0mb! Calculating averages with these values would not work as the calculation included the zeros. By inserting NULL the average only calculates based on the actual figures it has and returns the best value possible given the information it has. Not sure if there was a better way to solve this problem but it appears to be working ok for me at the moment.