I fully agree that MySQL should not parse and silently ignore constraints. It doesn't even generate a warning. I have sent feedback to the MySQL team in the past that this is a terrible bug, but it's too late at this point since changing the behavior would break millions of apps and web sites.
On the other hand, Oracle supports foreign key constraints -- except not cascading updates. Also, an empty
string in
VARCHAR2 is the same as a null, which makes them incompatible with ANSI/ISO SQL and every other vendor's implementation of SQL. This, they cannot fix? They've been the 2nd largest software company in the world for decades!
That's what I mean when I say every database has its idiosyncrasies.