ID Number: Q65963
1.00 1.10 4.20
OS/2
Summary:
This article explains how to calculate the amount of space needed for
the storage of NULL values.
More Information:
For all standard data types, NULL values stored by Microsoft SQL
Server do not take up any additional storage space. The only
associated overhead for a column containing a NULL value is a single
byte in the storage record that defines a pointer to the column. This
is a fixed cost that is associated with the creation of the column.
There is a special case for Text/Image storage.
If the columns were created with "nulls allowed," no additional space
is allocated for Text and Image columns until data is actually
inserted into those columns. However, once a Text or Image column has
had data inserted into it, the page space remains allocated even if
the column is changed to NULL. The only way to free this allocated
page space is to delete the row.
Additional reference words: 1.00 1.10 4.20