CALIS has exams for cataloging qualifications, in Chinese, Spanish, ancient books...
I don’t know much about public libraries, it seems they just take cataloging And classification training, once the training is passed, it will be gone.
However, the prerequisite for either method is to be able to enter the library first.
The above is for the work of cataloguers, which means that this position involves professional fields. As for the others...it doesn't matter if you understand library science or not, and it does not involve qualification examinations or anything like that.