   MySQL or MSSQL
  Hello,I'm writing a mmorpg, client is in C++ and server in C#.I was wondering what is the best database in terms of performances.I read up MSSQL got severals features that actually improves those perfomances, I also read up many articles "MySql vs MSSql" but I found the conclusion kinda..embarasing, people prefer mysql over mssql because of price.MSSQL express is a free version, It may doesn't contain all of MSSQL rich features, especially the one introduced in SQL Server 2008 but still, the express version is an serious alternative if you don't have money (like me).So, without the argument of price, which of those fit the best in an mmorpg server? Written in C#.Thanks   
  The bigger issue for MMORPGs is how well these databases support clustering and load balancing. Setting up a load balanced database cluster is far from a simple task, but there are some open-source tools that can help (mylbhelper, Ultra Monkey). I've also seen some articles about load balancing using MySQL replication and round-robin DNS.In addition to replication, MySQL also offers a full-fledged clustering solution using a different storage engine.  More info here. General info on MySQL availability. Documentation.On the other hand, Microsoft SQL Server 2008 Express edition does not scale at all. You're limited to a single CPU using 1 GB of RAM and 4 GB for database size. Neither Microsoft Cluster Server nor the other SQL Server editions have built-in load-balancing, so you'd have to once again rely on third party solutions (but I'm not aware of any open-source-based Microsoft SQL Server load balancing solutions) . So if you are only considering these two, MySQL seems to be the way to go.   ;  Although you didn't ask, I recommend PostgreSQL.It is BSD licensed (free and free) and has a .NET provider available.MySQL is overrated IMHO, because it offers a fast storage engine that a lot of people use for their websites; what you don't hear as often is that when you use that storage engine you lose data integrity, which is much more important for an MMO.Just my two cents, hope I didn't just start a religious war.   ;  I've heard good things about Postgres, especially from people using PostGIS for geospatial applications (ala Google Maps). Postgres Plus Advanced Server also supports clustering (GridSQL), so it sounds like a viable alternative to MySQL. That said, nobody forces you to use MyISAM in MySQL, although most people using MySQL for their websites probably don't know the difference. MySQL Cluster uses NDB so it's a different beast altogether.   ;  I don't think I'm going to add an argument between databases, however I do want to mention that MySQL isn't as free as you might think it is. You should really look into MySQL's licensing as it can be very expensive under certain conditions.For example, I was working on an application that I had planned on distributing a few years ago. I was looking at different database options and MySQL was one of my top picks. That was until I contacted them about distributing a copy of MySQL on my install disk with my application (I didn't want to tell my customers they had to go and download it from the MySQL site).Well, the licensing costs were somewhere around $270 per copy that I wanted to distribute. I was only planning to sell my software for $100-$150/copy so it really killed my idea to package MySQL with it.This was 2 years ago, so I'm not sure what has changed with the licensing, but if you are trying to decide on a database based on licensing costs (not specific features in the database itself), you should contact each of the vendors to find out exactly what you are getting into.Although from what I have read about the costs of running a MMORPG the cost of the database license will be the least of your expenses.John   ;  The exact interpretation of Sun's (soon to be Oracle's, I guess) dual license for MySQL is up to an IP lawyer, but my understanding is that you only have to pay licensing fees if you want to redistribute MySQL together with your own commercial, closed-source application. Of course, Sun may have a different view of that matter, so contacting them directly would work best.   