Which database if learning from scratch in 2010? [closed]

If you just want to be learning the SQL language, and not database administration, I would recommend working with SQLite. If you're on a Mac, it should already be installed. It is a much simpler system than most RDBMSes; there is no server to set up, and client to connect to the server. There are no directories of cryptic files, or anything of the sort. To get started, you can just type:

sqlite3 mydatabase.db

And start working with it. It's so much lighter weight and easier to set up and use than the other database systems that I think it's a good choice for a beginner.

Now, SQLite is a fairly small and lightweight language. If you need be getting into any kind of really complex queries and data mining, I would recommend PostgreSQL. It has a fairly advanced query optimizer, and a pretty long list of SQL features.

And if you want to learn a database as something to use for back-end storage for web programming or something of the sort, MySQL is what I'd choose. It's ubiquitous, supported by almost any web host, and it's pretty fast for very simple queries and updates, which is generally what you need for a web system. It has some real gotchas to avoid when setting it up; you have to choose between several different storage engines, and it can take a lot of work to convince it to actually work with Unicode data. But it's good to learn mostly for its ubiquity.

From what I've seen (at least on the web), MySQL and PostgreSQL are the most ubiquitous free database systems. If you're considering learning one of them, check this comparison out.

You may also want to consider learning SQLite, a "self-contained, embeddable, zero-configuration SQL database engine." It's really easy to get up and going, stored in a single file, and as its description says, has no complicated configuration. SQLite has proved enormously popular as a persistent data store for local apps on the desktop/iPhone. If you're going down this route on a Mac/iPhone, you may also want to check out Core Data, which is an abstraction layer Apple developed on top of SQLite(but can work with pretty much any DB), to simplify working with a database. As a bonus, Core Data includes a nice GUI for forming relationships and entities. You can check out this tutorial for more information.

If you really, truly, want to "learn from scratch", then theory is the first thing to learn. And that means : NOT products, not any. Not DB2, not MySQL, not oracle, not any-of-them.

Hugh Darwen has a freely available e-book entitled "An Introduction to Relational Database Theory". The material is quite "accessible" and quite unlike most other theory textbooks. It's also the accompanying textbook for his university course on database technology.

Chris Date has several books, of which "Introduction to database systems" is the most comprehensive, also the standard textbook in the field, but maybe a little too abstract for some.

If you think that all you need is "just to know a product" and that you can do equally well "without all that theory", then in that case, please disregard this response, because the wording of your question is dishonest.