At 10:30 Tuesday, 27.07.2004 +0000, burghard_w_v_britzke wrote:

>what is the longest varchar which can be indexed? it must be less than 255.

that depends on the character set used.
have a look at Ivan Prenosil's "index key size calculator":
http://www.volny.cz/iprenosil/interbase/ip_ib_indexcalculator.htm

HTH,
markus