Good Article on Database Abstraction 
August 13th, 2006, 11:10 pm by lig
Found this article through planet MySQL. In it he goes over 4 different “types” of abstraction layers that typically are collectively called a “database abstraction layer” - though they are very different from one another. I found it an interesting read.
His 4 types:
1. A software library to connect to a database server and issue queries, fetch results etc.
2. A software library to present a common API to different database servers.
3. A software library to automatically generate portable SQL queries.
4. A software library to map Object-Oriented Programming to a relational database (Object-Relational Mapping, or ORM)
