Netezza
has a special value called NULL. A Netezza NULL value means an absence
of information and is analogous to a SAS missing value. When
SAS/ACCESS
reads a Netezza NULL value, it interprets it as a SAS missing value.
You can define a column
in a Netezza table so that it requires data. To do this in SQL, you
specify a column as NOT NULL, which tells SQL to allow only a row
to be added to a table if a value exists for the field. For example,
NOT NULL assigned to the CUSTOMER field in the SASDEMO.CUSTOMER table
does not allow a row to be added unless there is a value for CUSTOMER.
When creating a Netezza table with
SAS/ACCESS, you can use the
DBNULL= data set option to indicate whether NULL is a valid value
for specified columns.
You can also define
Netezza columns as NOT NULL DEFAULT. For more information about using
the NOT NULL DEFAULT value, see your
Netezza Database User's
Guide.
Once you know whether
a Netezza column enables NULLs or the host system supplies a default
value for a column that is defined as NOT NULL WITH DEFAULT, you can
write selection criteria and enter values to update a table. Unless
a column is defined as NOT NULL or NOT NULL DEFAULT, it allows NULL
values.
To
control how the DBMS handles SAS missing character values, use the NULLCHAR= and NULLCHARVAL= data set options.