in the docs, the function "ascii(text)" is described as

returning "ASCII code of the first character of the argument"

(see
http://www.postgresql.org/docs/8.1/interactive/functions-string.html,
Table  9-6. "Other String Functions").

Presumably this should read "ASCII code of the first byte of the
argument",
which is what is returned when the argument is a multi-byte character
(although then with UTF-8 at least that might not necessarily be an
ASCII
code).

Ian Barwick