MYSQL update statement databases local & remote

[slasher]

Hi

I'm trying to update a local & remote database (i'll get on to this later)

1st tried a simple select statement

SELECT * FROM [SERVERNAME].[DATABASENAME].[DATABASE_USERNAME].[TABLENAME]

"Query empty"

can't get it to work

I'm using Navicat for queries

here is an example of what I need to do

update 
remotedb_books ,localdb_books
set 
remotedb_books.quantity=localdb_books.quantity
where
localdb_books.sku=localdb_books.sku

Can someone point me in the right direction

Thanks in advance

Dave