Truth table for AND comparisons:

2. Language Elements : Expressions : Operators : Logical Operators : Truth table for AND comparisons:

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	True	False	Null
True	True	False	null
False	False	False	False
Null	null	False	null

Truth table for OR comparisons:

	True	False	Null
True	True	True	True
False	True	False	null
Null	True	null	null

Truth table for NOT comparisons:

True	False	Null
False	True	Null

The order of precedence for these operators, from highest to lowest, is as follows:

NOT

AND

You can use parentheses to change this order. In the following example:

if (empnum > 0 or deptno > 0) and status != 3

OpenROAD first evaluates empnum and deptno and then evaluates status.

The following example illustrates the use of comparison and logical operators:

if empnum > 0 and status != 3 then
callframe newemployee;
endif;

The newemployee frame is called only if both conditions are TRUE, that is, if the current value of empnum is greater than 0, and status has any value other than 3.