which versions are you using (SonarQube, Scanner, Plugin, and any relevant extension)
what are you trying to achieve:
I want to develop a dashboard in Power BI to show some important information about projects scans, for instance when was the last time one scan was executed.
what have you tried so far to achieve this
We have executed some SQL sentences, but I don’t know if there is any documentation related to the description of each table and where I could get some information.
Do you know if there is any data dictionary to know where to get some insteresting statistics?
You should not query the SonarQube databse directly, it is a black-box that can change between versions without warning and its schema is not publicly documented – you should use the Web API (documentation linked in the footer of your instance). If you need help – take a look at this guide.