skjoldtc (2/20/2009)
The sparse column itself requires no space for storage if it contains a null value. However, additional storage space is required to store non-null values in the sparse column. That's why you don't get a 100% total space savings. In some cases the savings is pretty low.http://blogs.technet.com/andrew/archive/2008/02/28/sql-server-2008-sparse-columns.aspx
Please correct me if I'm wrong.
The weekend is here... nice. 😎
That's exactly as I understand it. The books-online stuff actually gives the approximate level of 'sparseness' (as it were) needed to achieve a 40% space savings.. So yeah a 'sparse' column that isn't actually sparsely populated with cells that contain non-null values, could very easily use more space.
I think the question however was as to the tickbox for the item that said that storing a null in a sparse column uses zero space, which based on the docs referenced above is TRUE