> is it possible to change default value of a column?

No and yes. (in that order ;)

There's no ALTER TABLE to do that, but you can do it via
two tricks:

- create a domain with a default and change your column to be of
that domain type instead of a raw datatype

or

- modify it by updating the system tables.

If you download Database Workbench ( www.upscene.com ) you
can change the default and it will generate the required statements
to do this.

Martijn Tonies
Database Workbench - tool for InterBase, Firebird, MySQL, NexusDB, Oracle &
MS SQL Server
Upscene Productions
http://www.upscene.com
My thoughts:
http://blog.upscene.com/martijn/
Database development questions? Check the forum!
http://www.databasedevelopmentforum.com