MySQL vs MSSQL

While they are very similar in capability (at least on a basic level), there are definite differences that can cause you problems or at least headaches.  For example, the syntax is different in some cases.  The classic example I like to give is:

MS SQL: SELECT TOP 10 * FROM MyTable
MySQL: SELECT * FROM MyTable LIMIT 10

As you can see, different.  And one will not work on the other.  90% is the same... but there are differences.

I would recommend you setup a local MySQL Database (it's free) and test your code against it.  Generally, when you develop something you should stick with the database platform you develop on.

While back when i was making some tests MSSQL was much faster than MySQL ...and somewhere on the Net i found a mention that MySQL was at its best on same performance level as SQL 2000...But in databases there are more lot things than single query performance...like good database design,licensing cost,clustering...unless you put the same load and run your tests you want get a definite answer.

I am going to chip in and say that if you are considering a database change, also look at Postgresql, as your host may support this too.

I've used both and like features of both.  They both have things that I wish were different than they are.

Out of the box, MySQL uses its own extensions to ANSI SQL that look a lot different than what you're used to.  Unless you're used to developing in MySQL you probably want to turn on ANSI mode.  The SQL will probably run slightly slower than the MySQL native SQL, but the conversion will be easier.  For simple queries the difference, if any, will be too small to be noticed.