how do I check for lower case - Mailing list pgsql-sql

I have a table with a column, lets call it identifier, that is defined
as varchar(8) that should never contain lower case letters.  Its a large
table.  Is there a way to query the table to see if any values in this
column are lower case and to get a list out?  The user interface
application that users use prevents them from adding an entry in lower
case  now, but didn't in earlier version.

Julie