I am looking for a publicly available SQL database with free access, where one can run some SELECT
queries for free on some meaningful data (not item1, item2, item3
I found SQLZoo which is something similar too.
I would suggest setting up Microsoft SQL Server 2008 Express (or the R2), and adding the Northwind or Adventureworks database. It's pretty big so I'm sure you can play with it.
If SQL Server is an option then Northwind/Adventureworks are the standard "training" DBs. Do a search.
For mySql this project looks promising:
http://sourceforge.net/projects/awmysql/
Also, this might be a dupe:
Is there a "Northwind" type database available for MySQL?
Where can I download Northwind database for Postgresql?
I like the concept of a game on pure SQL as implemented here: https://mystery.knightlab.com
It offers gamification of learning SQL and includes an optional tutorial-like introduction.
If you already know SQL but feel a little rusty, then this is fun to brush up.
For beginners it is an easy hand-help first contact.
The data are artificial and have a slightly steep drop-off when leaving the immediate game track, but I think it still matchs your requirement to be "meaningful". (And if you go intentionally off-track, then there are hints that some easter-eggs can be found, in the shape of jokes. I did not yet manage to get the query right to actually read them... So I think that even beyond the obvious game there is something for the more experienced to hunt for.)
I suggest to ask your government for some statistical data (just browse their website; there should be plenty). Then import the data in a H2 database and import it. Save the resulting DB files somewhere and give them to your students for their work.
If you're intersted, Eve Online, a rather large MMO, make their static data (in-game items, NPCs, anything that doesn't really change) available via download.
***edit:* http://www.eveonline.com/community/toolkit.asp
It's a very heavily normalized data set, with over a dozen table, and thousands of records. If you want to dive into the deep end of enterprise data warehousing, I'd recommend this.
Downloads as a MS SQL Server 2008 Backup file, which can be imported directly into MS SQL Server 2008 Express (The free edition)
I do not recommend this if you are brand new to databasing, however.