NEWB Getting to KNow New Database and Understand Where Relationships Are
I'm not a DBA but I've looked at many "new to me" databases.

I don't know if there is a trick to understanding a database.  What has worked for me is just to explore the db and query it to see what it returns.  

Many times as a new developer to a project I'm given a task to fix or update something.  I usually look at the table like you did with alert and look at any other id columns that might be in the table (i.e user_id &amp; incident_id).  That starts the bread crumb trail. Then I look at the foriegnkeys to see what they are doing (i.e. cascade delete).  The FK usually point to another table that could also lead to other tables.

If the bread crumb trail of id columns gets bigger than 2 or 3, then I usually try to diagram the db if possible.  Sometimes that helps me to see the tables in a different perspective.

Other than that, it just takes time.  As you get more tasks under your belt with the db you will understand more of it.