Missing values in logical expressions

In a simple relation, the logic is indeterminate if the expression on either side of the relational operator is missing. When two or more relations are joined by logical operators AND and OR, a missing value is always returned if all of the relations in the expression are missing. However, if any one of the relations can be determined, IBM® SPSS® Statistics tries to return true or false according to the logical outcomes. See the topic AND and OR logical operators for more information.

• When two relations are joined with the AND operator, the logical expression can never be true if one of the relations is indeterminate. The expression can, however, be false.
• When two relations are joined with the OR operator, the logical expression can never be false if one relation returns missing. The expression, however, can be true.