Oracle If Exists

CREATE OR REPLACE FUNCTION if_exists(value_in DUAL.DUMMY%TYPE DEFAULT 'X') RETURN INTEGER
IS
-- Test using: 
-- SELECT if_exists() FROM DUAL;
-- SELECT if_exists('X') FROM DUAL;
-- SELECT if_exists('Y') FROM DUAL;
 
    exists_boolean INTEGER;
BEGIN
    SELECT COUNT(*) INTO exists_boolean FROM dual WHERE dummy = value_in AND ROWNUM <= 1; -- Modify the FROM and WHERE as needed.
 
    RETURN exists_boolean;  -- If exists then 1 else 0.
END;
/
 
SELECT if_exists() FROM DUAL;
SELECT if_exists('X') FROM DUAL;
SELECT if_exists('Y') FROM DUAL;