When two or more relations are joined by logical
operators AND or OR, the program always returns a missing
value if all of the relations in the expression are missing. However,
if any one of the relations can be determined, the program interprets
the expression as true or false according to the logical outcomes
below. The asterisk flags expressions where the program can evaluate
the outcome with incomplete information.
Table 1. Logical outcomes
| Expression |
Outcome |
Expression |
Outcome |
| true AND true |
= true |
true OR true |
= true |
| true AND false |
= false |
true OR false |
= true |
| false AND false |
= false |
false OR false |
= false |
| true AND missing |
= missing |
true OR missing |
= true* |
| missing AND missing |
= missing |
missing OR missing |
= missing |
| false AND missing |
= false* |
false OR missing |
= missing |
|