MySQL is a multithreaded, multi-user SQL database management system (DBMS) which has more than 11 million installations. The program runs as a server providing multi-user access to a number of databases.
MySQL was owned and sponsored by a single for-profit firm, the Swedish company MySQL AB, now a subsidiary of Sun Microsystems, which holds the copyright to most of the codebase. The project's source code is available under terms of the GNU General Public License, as well as under a variety of proprietary agreements.
The relational database management system (RDBMS) officially called Oracle Database (and commonly referred to as Oracle RDBMS or simply as Oracle) has become a major presence in database computing. Oracle Corporation produces and markets this software.
Larry Ellison and his friends and former co-workers Bob Miner and Ed Oates started the consultancy Software Development Laboratories (SDL) in 1977. SDL developed the original version of the Oracle software. The name Oracle comes from the code-name of a CIA-funded project Ellison had worked on while previously employed by Ampex.
Advantages of MySQL over Oracle :
MySQL is characterised as a fast, robust database with a good feature set, but one which lacks all the extras of something like Oracle ... so if you're writing code that's designed to be portable it's a pretty good choice. Admin / security are effective but the setup of these and othe features isn't over-complicated. All in all, a pretty good choice for many "middle of the road" requirements.
MySQL is characterised as a free, fast, reliable open source relational database. It does lack some sophistication and facilities, but it has an active development team and, as it goes from release to release, more capabilities are added. At certain times there will be a trade-off between speed and capabilities, and the MySQL team intend to keep their database engine fast and reliable.
Advantages of Oracle over MySQL :
Oracle is much versatile than MySQL. Oracle can run and handle more transactions than MysQL. Oracle would be better if you are going to have lots of db usage.
I've used MySQL. Only for a forum. Still, MySQL takes up resources with PHP that affected the server load. Oracle on the other hand is better with memory leaks and handles multiple threads. You can do SQL Transactions, stored procedures, DTS in Oracle that you can not do in MySQL earlier versions.
Oracle is expensive, although they came out with Oracle Free Edition to attract MySQL users.
MySQL users enjoy this database because it is available on virtually all hosting companies. Oracle are only limited to large corporations due to licencing costs and not all hosting companies have Oracle (they might have SQL Server, but not Oracle).
You can make billions of data with MySQL, but it will be slow on the server. In addition, backing up the MySQL database takes forever, versus Oracle's tools which makes database backup a cinch.
If you are going to use MySQL, then add lots of memory. In addition, I recommend that you seperate the Website from the database. In other words, have emails and website on a seperate server and only have a dedicated MySQL server specific to mysql/db only.
MySQL is Free, It's everwhere, that's the whole concept!!!