2 thoughts on " Three-valued Boolean Logic " Kombajn zbożowy November 9, 2013 at 7:43 pm. Excellent post. Good start! Possibly NULL logic would be far more clear if Oracle (and other engines) maintained consistent behavior regarding NULL handling in their functions."DECODE compares a column or expression to search values, returning a result when there is a match. DECODE is similar to IF_THEN-ELSE logic." Decode SQL represents one of the most powerful of all of the BIFs. Oracle decode SQL is used within the Oracle database to transform data values from one value to another.
"unknown" is not a boolean value in three valued logic. The boolean values are TRUE, FALSE, NULL. In Oracle when a column is null (i.e. holds no value) the absence of a value could have several meanings (other than "unknown"). At this point one should remember that in SQL, as well as in the relational theory, three-valued logic is used. That means the true value of a comparison operation can be not only TRUE or FALSE, but also UNKNOWN. Three-valued Boolean Logic The Three-eyed Raven likes it by Przemysław Kruglej 11-2013 przemyslawkruglej.com [email protected] 1