In any case, the code is not repetitive, so it is case-insensitive. However, you should pay attention to one thing. For varieties with two letter codes, Zhengzhou Stock Exchange uses three numbers to represent the year and month. For example, rebar (Shanghai) is RB 16 10, but sugar (Zhengzhou) is SR609 instead of SR 1609, but four numbers are still entered for the one-letter one. Now some software circumvents this problem by default, while others don't. Just pay attention to this piece