Fabien,
> Moreover, there are many SQL flavors around, so whatever the detailed
> syntax I learn them, it won't be the one they will have to face if the
> database they use is different. So why bother?
There are so many Java flavors around, why bother teaching the students syntax
at all? The flavor they work with in your class will probably be different
from what they have on the job.
See my point?
One of the primary reasons for the existence of international standards is
education. If you stick to Beginning & Intermediate SQL92, you can give your
students a set of SQL syntax that they can use on 80% of the RDBMSes in
service, including Postgres, HSQLDB, SQLite, Oracle, and SQL Server. This
is serving them well.
Were I teaching a class with a SQL component, using PostgreSQL as a tool, I
would be very careful to avoid letting my students use an extensions to SQL;
no "!=", no "SELECT DISTINCT ON" and no alias references in the GROUP BY
clause.
Allowing your students to use a non-standard operator that will fail them the
instant they leave the classroom is serving them badly indeed.
--
Josh Berkus
Aglio Database Solutions
San Francisco