Function to specify an alternative value for an empty expression
The EVL() function evaluates the expression in <expr1>, and if the expression does not evaluate to an empty value, the evaluated result is returned. If the expression in <expr1> does evaluate to an empty value, the expression in <expr2> is evaluated. If <expr2> does not evaluate to an empty value, the evaluated result is returned. If both <expr1> and <expr2> evaluate to an empty expression, the NVL() function returns 0.
CREATE TABLE contact (firstname c(20), lastname c(20)) INSERT INTO contact (lastname) VALUES ("Smith") SELECT lastname, evl(firstname,"Unknown") from contact