You use logical operators to combine boolean expressions into a larger boolean expression. The result is always true or false:
|
Operator |
Meaning |
Example |
|---|---|---|
|
NOT |
Logical negation. If A is true, NOT A is false. If A is false, NOT A is true. |
NOT Price = 100 |
|
AND |
Logical and. A AND B is true if both are true. A AND B is false if either is false. |
Tax > 3 AND Ship < 5 |
|
OR |
Logical or. A OR B is true if either is true or both are true. A OR B is false only if both are false. |
Tax > 3 OR Ship < 5 |
When you combine two or more boolean expressions to form a new expression, the new expression is either true or false. The following truth table shows how true and false expressions are evaluated to form an expression that is either true or false.
For example, if "My dog has fleas" is true and "My hair is brown" is false, then "My dog has fleas OR my hair is brown" is true, and "My dog has fleas AND my hair is brown" is false:
|
If one expression has this value |
And the logical operator is |
And if another expression has this value |
The resulting expression has this value |
|---|---|---|---|
|
TRUE |
AND |
TRUE |
TRUE |
|
TRUE |
AND |
FALSE |
FALSE |
|
FALSE |
AND |
TRUE |
FALSE |
|
FALSE |
AND |
FALSE |
FALSE |
|
TRUE |
OR |
TRUE |
TRUE |
|
TRUE |
OR |
FALSE |
TRUE |
|
FALSE |
OR |
TRUE |
TRUE |
|
FALSE |
OR |
FALSE |
FALSE |
|
NOT TRUE |
AND |
TRUE |
FALSE |
|
NOT TRUE |
AND |
FALSE |
FALSE |
|
NOT FALSE |
AND |
TRUE |
TRUE |
|
NOT FALSE |
AND |
FALSE |
FALSE |
|
NOT TRUE |
OR |
TRUE |
TRUE |
|
NOT TRUE |
OR |
FALSE |
FALSE |
|
NOT FALSE |
OR |
TRUE |
TRUE |
|
NOT FALSE |
OR |
FALSE |
TRUE |
If you use a logical operator with a boolean function that returns null, the term with the null return value is evaluated as false. If you use the NOT logical operator with a boolean function that returns null, the complete term evaluates to true. For example, NOT gf_boolean () evaluates to true when gf_boolean returns null.
