The processing behavior of a
null value depends on the mode, which is determined by how you connect to SAS Federation Server.
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A client application that connects to SAS Federation Server with a client-side
driver processes data by default by using
ANSI SQL null value behavior.
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When you use SAS Federation Server LIBNAME engine, 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.
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You can sort a SAS missing value and evaluate it with standard comparison operators.
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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 <.
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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).
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Many relational databases, such as Oracle and DB2, implement ANSI SQL null values.
Therefore, the concept of ANSI SQL null values with the SAS Federation
Server languages is the same as with the Oracle SQL language.
Note: Because the SAS data set
does not physically store null indicators, SAS Federation Server languages
emulate ANSI SQL null values for the data source.