Cut out the middle man
How often do you end up with multiple Excel files for an analysis, each subtlely different? Never sure which is the correct file? Daren't delete any, just in case?
With a relational database, this is a dilema of the past. Your data set for analysis is created using queries stored in the database. No duplicate is made of the data, but instead you link to the query directly from your statistical or GIS package.
All leading stats packages such as S-plus, Genstat and SAS can connect directly to databases in this manner, as can the Arcview and Arc/Info GIS systems.