It is going to be up to you to get the queried worked out properly but based on what you have posted it might look something like this:
SELECT * FROM users
JOIN clients ON users.userID = clients.userID
JOIN notes ON clients.clientID = notes.clientID
WHERE users.userID = colname
ORDER BY date_column DESC
LIMIT 5
colname would be defined as:
name: colname
type: number
default value: -1
runtime value: <your current user's id session variable>
This is just an example of course and you would need to alter this to fit your needs but it should help you to get the proper query in place. Here is a link to the w3schools on how to create JOIN statements:
sql_join.asp
