Nulls require variable length datatypes

Only columns with variable-length datatypes can store null values. When you create a NULL column with a fixed-length datatype, Adaptive Server converts it to the corresponding variable-length datatype. Adaptive Server does not inform you of the type change.

Table 8-2 lists the fixed-length datatypes and the variable-length datatypes to which Adaptive Server converts them. Certain variable-length datatypes, such as moneyn, are reserved; you cannot use them to create columns, variables, or parameters.

**Table 8-2: Conversion of fixed-length to variable-length datatypes**
Original Fixed-Length Datatype	Converted To
char	varchar
nchar	nvarchar
binary
datetime	datetimn
float	floatn
int, smallint, and tinyint	intn
decimal	decimaln
numeric	numericn
money and smallmoney	moneyn

Data entered into char, nchar, and binary columns follows the rules for variable-length columns, rather than being padded with spaces or zeros to the full length of the column specification.