The top 7 free databases are generally :
I am personally biased towards Firebird right now. This is for the same project for which I was considering SQLLITE :
Turns out even SQLLite does not measure up to the extreme level of performance I demand of my application. So I need some easy to distribute yet high performance SQL for Windows Database.
Normaly I would turn to mysql but since its oracle acquisition I don't trust it. (not that I hate oracle ... it's just a conflict of interest in my opinion). Check out the following to see what I mean:
Note that the original creator of MySQL forked into MariaDB so that should be something to look out for ... but for now its just too much hassel for being RAD :). Not to mention that its not free (GPL) for commercial use.
Firebird is supposed to have good design time support for .NET:
However its .NET portal seems a bit dated (feel free to check me ... i hope to be wrong here) :
And I couldn't find the embedded version it speaks of.
Anyways I will try out the server version and try to get it to work portably. Will update on it later :)