为PL/SQL中的函数提供字符串

FUNCTION concatenate_strings(str1 IN VARCHAR2, str2 IN VARCHAR2) RETURN VARCHAR2 IS
BEGIN
  RETURN str1 || str2;
END;

FUNCTION replace_string(input_str IN VARCHAR2, old_str IN VARCHAR2, new_str IN VARCHAR2) RETURN VARCHAR2 IS
BEGIN
  RETURN REPLACE(input_str, old_str, new_str);
END;

FUNCTION substring(input_str IN VARCHAR2, start_pos IN NUMBER, length IN NUMBER) RETURN VARCHAR2 IS
BEGIN
  RETURN SUBSTR(input_str, start_pos, length);
END;

FUNCTION number_to_string(num IN NUMBER) RETURN VARCHAR2 IS
BEGIN
  RETURN TO_CHAR(num);
END;