Programming Guide - Actian

ExpressionsHowever, you cannot use the following statement:if x = null ...Instead, you must use the following statement:if x is null ...If you set the value of a reference variable to null, the reference variable is nolonger associated with an object. (OpenROAD frees any object that does nothave at least one reference variable pointing at it.)The ifnull function and the is null operator provide you with ways to handlenulls in expressions. For more information about the is null operator, see Is[Not] Null Operator (see page 46).ExpressionsExpressions are language constructs that resolve to a value, a set of values, orTRUE or FALSE. Expressions can contain a wide variety of language elements.For example, you can use:• Literals• Variables• Named constants• Values returned by procedures• Arithmetic and string expressions• Logical (boolean) expressionsIn addition, OpenROAD lets you use all the operators and functions of theIngres DBMS.Expressions are used widely in 4GL. For example, the value of an expressioncan:• Be assigned to an OpenROAD variable• Be used as part of a search condition in a query statement• Serve as a condition in an OpenROAD if or while statementThe following subsections describe the language elements that you can use inexpressions.36 Programming Guide