6.9 Additional Topics

In this short chapter, I have not mentioned several topics that are of considerable importance in database work:

• SQL has only been demonstrated, not fully laid out. It's a fairly simple language; if you'll be doing much database work, you should read the language manual that comes with your DBMS carefully , and look at several examples. Tutorial books are also available for most popular DBMS.

• Transactions are loosely defined as a set of database queries and modifications that belong together. For example, you may enter a new gene into your database by updating several relevant tables. If your system should experience a failure in the middle of such a set of updates, it can leave your database in an ill-defined state. By defining transactions, it's possible to avoid such undesirable states, and many DBMS now provide support for this view of database updates.

• Entity-relationship modeling is a top-down design methodology with a fairly simple graphics representation that signifies relationships between the data in a system.

• Stored procedures are parts of a database application that are performed at the point of entry when a user is filling out a form for instance. MySQL is just now starting to support them; major DBMS such as Oracle have had them for a long time. They tend to improve performance of an application when used well; they also greatly increase the difficulty of migrating to a different DBMS if that becomes necessary in the future.

• Object-oriented and object-relational databases are new data models that are finding some acceptance. You may come across them on the job, although their use is much more limited than the standard relational model.