Where are matrices used in real life

Databases in everyday life

You can use different tools like SQLMAP etc. to be able to grant access to the databases in the case of insecure php = id1 pages. As some who deal with the topic know, there are hardly any of these pages, at least not in the case of new pages. I have two questions about this, a theoretical question and a practical one:

Is it possible to grant access to Internet pages of any kind or PhP that are new (even as long as you are not Geohot or a professional hacker), can someone suggest a theoretical video or explain how it works in theory if you are using SQL Injections can still hack databases?

And maybe how can you put that into practice in order to hack databases. Do the classic Linux SQL tools still work with new pages, what alternatives are there to hack databases?

In a video from ComputerPhil (a very good channel in my opinion, because it explains a lot of theory) talked about SQL injections that are no longer properly possible and that is only theory for old websites.

I am mainly interested in the theory behind how hackers access databases or "bypass" log-in fields with the help of the contents of the databases.