SQL Server 2005: Bit, Image, VarBinary, and unsigned numeric data types


If you use bit, say to represent a boolean value, you are actually not allocating 1 bit but 1 byte.  The first bit will give you 1 byte and the next 7 bits will use that byte so if you declared 8 columns in your table of data type bit, they will all share the same byte.  If these are all nullable, or just even one, another byte is allocated.  So if you don’t need your bit to be nullable, then make sure it’s not.

Image and VarBinary

Image data type is used for backwards compatibility in SQL Server 2005 and varbinary(max) is the replacement for it, which is essentially a LOB (large text or binary object) field that can take up to 2^31 bytes of data.  If you don’t want this a big of a size, you can specify a length for a varbinary data type up to a maximum of 8,000 bytes only.

Unsigned numeric data types

SQL Server 2005 (or SQL Server for that matter) does not have a concept of them.


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