Tests for a missing value.
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sql-expression IS <NOT> NULL | MISSING
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- sql-expression
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is described in sql-expression.
IS NULL and IS MISSING are predicates that test for a missing value.
IS NULL and IS MISSING are used in the WHERE, ON, and HAVING expressions.
Each predicate resolves to true if the sql-expression's result is missing
and false if it is not missing.
SAS stores a numeric missing value as a period (.) and a character missing
value as a blank space. Unlike missing values in some versions of SQL, missing
values in SAS always appear first in the collating sequence. Therefore, in
Boolean and comparison operations, the following expressions resolve to true
in a predicate:
3>null
-3>null
0>null
The SAS method for evaluating missing values differs from the method
of the ANSI Standard for SQL. According to the Standard, these expressions
are NULL. See sql-expression for more information on predicates and operators. See
PROC SQL and the ANSI Standard for more information
on the ANSI Standard.
Copyright © 2010 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
