Which database for dating site? MS sql or mysql ? Please advice

depends on what your host supports

If you're running Windows, you can choose either. If you have a linux host ( running Apache ) then you're limited to MySQL.

MySQL is the best, If i recall MS SQL sucks.

Linux is always better then windows (and cheaper), so MySQL will be the most effective way to go.

what is the difference between mssql and mysql?

It depends on which version of each. MySQL before v5 didn't allow stored procedures. I think it still doesn't have indexed views. Common installations are free, although some of the engines are as pricey as SQL 2005 standard edition. The Microsoft version tends to be a bit more featured: in v9 you can write stored procedures in C++ or VB, there are great ranking and pivot/unpivot functions built into the T-SQL language, graphical execution plans ... nice stuff. I don't know how MySQL does with XML natively?

If you use MySQL, you should use 5.x and procs. In that case, for the basics, they aren't all that different.

MySQL will turn out to be less expensive and easier to maintain in the long run.
If your proposed website is going to be in PHP, it makes the MySQL case even stronger.

PHP and MySQL are like "made-for-each-other", quite similar to the agenda being persued in your dating website ?

--Amit.