I'm sure I'm doing something stupid here, but i've been struggling with this query for ages so I've got to give up and ask!

I have two tables that i'm trying to create a report with. 

1.  A users table, with two columns - a user ID and a staff member name

2.  A time entries table with 3 columns - the user's id, the date, and the number of hours

(i've simplified the tables to just the columns i'm worried about)

I want to run a report that allows us to see who hasn't filled out their time for any given month.  So that means that if Table 1 has these entries:

user_id_1     UserName1

user_id_2     UserName2

user_id_3     UserName3

and Table 2 has these entries

user_id_1    1-8-09      4

user_id_1    2-8-09      5

user_id_3    5-8-09      5

After grouping by month, I would like a report that says:

UserName1    9 (hours)

UserName2    null

UserName3    5

Here is the SQL query that I have at the moment:

   

    
SELECT "Users"."Staff Member Name" AS "Staff Member", "Time Entries"."Activity" AS "Activity", "Time Entries"."Hours" AS "Hours", WEEKOFYEAR("Time Entries"."Date") AS 'Week'
    


    
FROM "Users" 

    


    
LEFT JOIN "Time Entries" on "Time Entries"."Added User" = Users."User ID"
    


   

UserName1  1-8-09      4

UserName2  1-8-09      4

UserName3  1-8-09      4

UserName1  2-8-09      5

UserName2  2-8-09      5

UserName3  2-8-09      5

etc.  -- it seems to be repeating each line entry for each person listed int he User table, rather than just listing the users who haven't got any matching entries with a null value.

Can someone help me figure out where I'm going wrong? 

Thank you very much!