In writer, when you are doing mailing, there is a way to select a calc file as
the database. Doing this, Writer will automatically create a database file
(odb). Then, you can access to it from the database tool (pressing the f4 key).

In calc, we can use the database tool (pressing the f4 key), we can access to
the already defined databases. But there is no way to add a database by
selecting a Calc file and auto-generating the database file (odb).

To do this, I need to use Writer or to use Base to create it. A nice enhancement
would be to directly do so in Calc.