Repository query for character set

I am running some SQL queries against the er/studio repository, but I can't work out how to extract the character set information for an attribute. I have looked at the sample SQL repository queries but they don't help in this case. I think the character set information is in PROPERTY_VALUE_USAGE_VER but I can't work out the relationship between this table and  ATTRIBUTE or ENTITY. Any information on how to do this would be useful.