NULL values or Zero in numeric fields?

We have a few tables with numeric columns. By default, if you don't save a value in those columns, they are NULL values. Is there an advantage to leaving these empty rows as NULL? Users that are doing queries directly against the database are asking that Zero be put in the rows where no value has been specified. Programmers find it annoying to have to make sure that calculations are not done on NULL values since it returns a NULL if you do.

What does that do as far as data storage is concerned? Will a zero take more space then a NULL?

Thanks for any help that you can provide.

+===================================================================+


+                                                                   +

+    Francois Lachance                                              +

+    Data Administrator                                             +

+    Saskatchewan Highways and Transportation                       +

+    Regina, Saskatchewan                                           +

+    Canada                                                         +


+                                                                   +

+===================================================================+