personal advice can go to the Internet to watch videos directly, many of which are free about databases. Better learning websites are: Mutu.com, Tencent classroom, NetEase Cloud classroom and so on.
take mysql database as an example. I learned it in Tencent class. It feels good. I'll give you a link https://ke.qq.com/course/280048

it is not recommended to learn through blog

go through the basics systematically:
SQL tutorial
MySQL tutorial

check the corresponding official documents
mysql
sqlserver

blog is only used as a place to query solutions to difficulties

1. first learn the basics of mysql and understand the basic sql writing syntax
2. Advanced can read the book "High performance mysql"