oracle自定义函数的执行时间

  if (len = 15) then
    -- 检查是否全为数字，否则转换操作会抛异常，导致程序崩溃，ascii('0') = 48, ascii('9') = '57'
    --for i in 1 .. 15 loop
    WHILE i <= 15 LOOP
        --ch := substr(id, i, 1); -- 非数字会报错
        c := ascii(substr(id, i, 1));
        if c < 48 or c > 57 then
            exit;
        end if;
        i := i + 1;
    end loop;

    IF i = 16 THEN
        trans := TRUE;
        ret := '19' || substr(id, 7, 2);
    END IF;
  end if;

  if (len = 18) then
    -- 2006-10-18 luocm
    -- 检查是否全为数字，否则转换操作会抛异常，导致程序崩溃，ascii('0') = 48, ascii('9') = '57'
    --for i in 1 .. 17 loop
    WHILE i <= 17 LOOP
        --ch := substr(id, i, 1); -- 非数字会报错
        c := ascii(substr(id, i, 1));
        if c < 48 or c > 57 then
            exit;
        end if;
        i := i + 1;
    end loop;

    c := ascii(substr(id, 18, 1));
    --if i <> 18 OR (c <> 88 AND c <> 120) OR c < 48 or c > 57 THEN -- 第18位为[0-9xX]
    if i = 18 AND (c = 88 OR c = 120 OR c >= 48 or c <= 57) THEN -- 第18位为[0-9xX]
        trans := TRUE;
        ret := substr(id, 7, 4);
    end if;
  end if;

  IF trans = FALSE THEN
      i := 1;

      WHILE i <= 8 LOOP
        c := ascii(substr(birthday, i, 1));
        if c < 48 or c > 57 then
            exit;
        end if;
        i := i + 1;
      end loop;

      IF i > 8 THEN
         yyyy := substr(ltrim(rtrim(birthday)), 1, 4);
         IF yyyy < 1900 OR yyyy > 2000 THEN
            ret := '';
         ELSE
            ret := yyyy;
         END IF;
      ELSE
         ret := yyyy;
      END IF;
  END IF;

  RETURN ret;
end f_extract_birthday;

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