Kbase P32742: Results of using the unknown value '?' in logical expression
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
15/10/2008 |
|
Status: Verified
GOAL:
Results of using the unknown value "?" in logical expression
GOAL:
Comparisons with UNKNOWN
FIX:
How does the use of the unknown value "?" evaluate in a WHERE clause or other logical expression? First of all, the unknown value is simply that - unknown. It is neither true nor false.
For example:
DISPLAY (1>?)
yields a result of "?" because it is unknown whether 1 is greater than the unknown value.
Likewise:
DISPLAY (1=?)
yields false. We know that 1 is equal to 1, and but that is the best we can say without a doubt.