The processing behavior of a null value
depends on the mode, which is determined by how you connect to the
DataFlux Federation Server.
-
A client application that connects
to the DataFlux Federation Server with a client-side driver processes
data by default by using ANSI SQL null value behavior.
-
When you use the SAS LIBNAME engine
for DataFlux Federation Server, null values are processed by default
with SAS missing value behavior.
In some ways a SAS missing
value is analogous to an ANSI SQL null value; however, the processing
behavior can be different. Therefore, if an application is processing
data with SAS missing value behavior rather than ANSI SQL null behavior,
then you need to be aware of processing differences.
-
You can sort a SAS missing value
and evaluate it with standard comparison operators.
-
You cannot sort an ANSI SQL null
value or evaluate it with standard comparison operators, because there
is no data on which to operate. For example, to test for a null value,
you cannot use arithmetic comparison operators such as = or <.
-
SAS missing values in a SAS data
set are translated to ANSI SQL null values when the data is copied
to a data source that processes in the ANSI SQL null mode (for example,
an Oracle database).
-
Many relational databases, such
as Oracle and DB2, implement ANSI SQL null values. Therefore, the
concept of ANSI SQL null values with the DataFlux Federation Server
languages is the same as with the Oracle SQL language.
Note: Because the SAS data set
does not physically store null indicators, the DataFlux Federation
Server languages emulate ANSI SQL null values for the data source.