> found out about index key size the hard way yesterday, so now I'm
> trying to reduce field sizes to the minimum.
> isn't there a way to reduce the size of a varchar field by SQL?

No.

> I tried this here ("Vorname" is of size 60 now):
> >>ALTER TABLE "Divers1" ALTER "Vorname" TYPE VARCHAR(40)<<
> but got an error ("must be at least 60").

Create a new field, pump data, drop old field, rename new field.

With regards,

Martijn Tonies
Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL
Server
Upscene Productions
http://www.upscene.com