After going thru some tutorials on SQL Server 2008's new feature "SPARSE COLUMN", I have found that it doesn't take any space if the column value is 0 or NULL but when there is a value, it takes 4 times the space a regular(non sparse) column holds.
If my understanding is correct, then why I will go for that at the time of database design? And if I use that, then at what situation will I be?
Also out of curiosity, how does no space get reserved when a column is defined as sparse column (I mean to say, what is the internal implementation for that?)