Underline examples: - Identifier declaration - Error message - Warning message - Information message CREATE OR REPLACE FUNCTION ...

| -- Underline examples:
  -- Identifier declaration
  -- Error message
  -- Warning message
  -- Information message
  CREATE OR REPLACE
    FUNCTION booleantochar ( is_true BOOLEAN)   RETURN VARCHAR2
    AS
      BEGIN
        IF( is_true )
          THEN
            RETURN 'TRUE';
          ELSIF  NOT ( is_true )
          THEN
            RETURN 'FALSE';
          ELSE
            RETURN TO_CHAR (  NULL  ) ;
        END IF;
      END booleantochar;|