A
null value indicates the absence of information. A null value means
that a real value is unknown or nonexistent. That is, no data is assigned
to the column in that specific row. A null value is not a zero or
a blank, and it does not behave like a zero or a blank.
A null value is represented
by the DataFlux Federation Server either as a SAS missing value or
an ANSI SQL null value:
The SAS missing value
indicators ( . , ._, .A-.Z, and ' ') are known values that indicate
nonexistent data. A SAS missing value is interpreted as its internal
floating-point representation. By default, SAS prints a missing numeric
value as a single period (.) and a missing character value as a blank
space. A SAS data set represents null values with SAS missing values.
Table data with an
ANSI null has no real data value; it is metadata that indicates an
unknown value. Third-party relational databases represent null values
with ANSI SQL null values.