Hi, I was comparing between Access, MSDE and MySQL and I read somewhere that Access supports about 5 concurrent users, MSDE with 15 (if I remember correctly from MS website) and not sure about MySQL.

So what counts as "concurrent users"? Is it users that submit queries to the database and such that the database interleave the processing of those queries and resultsets?

Actually I have developed a web app that is base on Access that allows users to update records in the database in the intranet. The number of users for update is around 40. But I just expect the worst case (40 users all access at the same time) in the intiial stage when they need to input quite number of records. The records is within 2k (as Access restricts it) and the web app uses connection pooling. Would there be a good chance that the update users would overload the database? Would I need to consider other db such as MSDE or MySQL?

Thanks!

The limit on MS-Access is mostly technical, since the Jet database engine itself is the limiting factor. If you buy a big enough machine (for example, an IBM blade server, backed by an EMC SAN), you could support 40 simulataneous users, but the cost would be astronomical!

The limit for MSDE is mostly software licensing. There is also a query governor that limits performance of the engine after the fifth active query starts, but that is purely artificial because the engine itself (SQL Server) can handle several hundred active queries at the same time if the hardware is up to it.

The limiting factor for MySQL is usually the person doing the installation or the available hardware, there isn't really any software limit built into the system. Current versions of MySQL that are properly installed on reasonable hardware can support 40 simulataneous queries. There are a lot of conditions in that sentence, but if you meet them all, MySQL can do what you want.

If you are building this site purely for fun (not business), and don't need paid technical support, MySQL is a very good choice. If you are building this site for business, then I'd recomment MSDE for development, but be ready to buy MS-SQL if testing shows that you need better performance.

-PatP