I'm trying to find an SQL statement that will prepend a string to a
field for a certain set. That is, for a certain set of rows, I want to
prepend the string '100' to the beginning of a certain field. Here's
what I've tried:

update mytable
set mycolumn = '100' + mycolumn
where .... {some where clause}

This seems to have absolutely no affect. The 'mycolumn' field stays
exactly the same, but I get no error either.

How can I do this?

Thanks,
Joe