First, string
is not a valid date type. You need varchar2
instead. Second, strings are delimited by single quotes not double quotes.
It would appear, therefore, that you want
CREATE OR REPLACE FUNCTION refreshment( p_code IN VARCHAR2 )
RETURN VARCHAR2
IS
BEGIN
RETURN CASE p_code
WHEN 'H' THEN 'Hot'
WHEN 'C' THEN 'Cold'
WHEN 'N' THEN 'None'
END;
END;