$validationRules is there a documentation with all the references we can use?

Hi, I always find myself browsing the web to find how to write validation rules. Is there a documentation somewhere I haven't yet found that might list all the available rules we can use depending on the database expected data format? Or can I find it within the code? (and maybe suggest/write a little addition in the documentation that could be useful for beginners and people like me?)
Thanks

(I found this from some versions ago that is a beginning https://www.codeigniter.com/userguide2/l...ereference but I think there is more to it and there might be some changes)