Is there actually much difference between them and also what is the point in them? Is it worth learning them both or not is another question I have?
l advice MySQL, l am not a coder, programmer, but MySQL is open source and free as l know and MSSQL belongs to MS? So l would prefer MySQL.
There's a huge difference between MySQL and MS-SQL Server. Not to start a big flame war but MS-SQL has far more professional features in it than MySQL does. MySQL is good for simple databases but if you're doing a serious database then you want to be looking at a professional level database: Oracle, MS-SQL or Postgre. You can learn SQL on any database. The complex bits: PL/SQL, DB Administration, Backup and Recovery, etc. are more database specific.
All decent databases use the same basic principles (so if you learn one you can pick up the basics of another pretty easily), hence, Standardized Query Language. However, all of the major players expand on the basic stucture and add their own features (Transact-SQL for MS-SQL, P/L for Oracle, etc...). These features and functions are unique to that platform (though there may be something on other platforms that is directly comparable but may be called something else). The question is what you are planning on doing with it. From a purely operational standpoint, you would need to have a very large and complex database to go beyond the limits of the latest MySQL releases. From a database designer/administrator perspective, MySQL doesn't come close to MSSQL or Oracle. That has little to do with the SQL engine itself, rather the tools they come with. I have to disagree that MySQL is not for serious databases. The Google AdWords system is MySQL driven. They tried to move to a commercial system and went back to MySQL. And MySQL closes the gap with every release. If you are just going to be making small websites by yourself I wouldn't bother with MSSQL. It costs money and I think you will find that most hosts you want to use and most php scripts you might buy are configured for MySQL. If you want to be a database admin, then start with MSSQL (but you can still learn MySQL).
Microsoft SQL Server 2005 has a free version that you can use with their extremely powerful development tools (also free). I use it to run hundreds of websites without a problem. The free development and management tools are limited compared to the enterprise versions, but if you learn to script the SQL, all those limitations are removed because you can perform actions from the command line.
I know it's quite an old edition, but SQL Server 2000 was my main experience at database administration. I cut my teeth on MySQL. Admittedly, I've never used another DBMS since SQL2k, but I prefer MySQL. It just works... nicer? Dunno.. someone give me a copy of oracle
MySQL is a joke in most large companies...companies that DO use MysQL also use MySQl in conjunction with another database like Postgres or Oracle Companies that don't like using Microsoft products would go with Postgres and Oracle and pro microsoft companies would go with SQL Server But if you are starting out, MySQL is fine
I used MySQL but recently moved to MS SQL 2005. As my applications become more complex I more and more limitaions in MySQL. Nowdays it is not a problem find a hosting provider who offer MS SQL and there is free version for local development too.