If you have a 250Mb Db which only contains 30Mb of data. Then the backup should be around the 30Mb mark give or take.
A database being 250Mb in size, most likely would include data, transaction log and unused space. Your transaction log is not included in a full database dump. And the space allocated to your db which is not currently filled with data is also not backed up.
I'm sure the answer also depends on your version of SQL Server as well. Does this answer your question?
Originally posted by ssivaprasad
If a 250 MB database contains only 30 MB of data, how much of the database is written when the database is backed up? Why?
a. 30 MB
b. 250 MB
c. 220 MB
d. 60 MB