SQL & PL/SQL :: Group Results By Date With Running Totals?

My version of the Database:

BANNER
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bi
PL/SQL Release 10.2.0.5.0 - Production
"CORE10.2.0.5.0Production"
TNS for Linux: Version 10.2.0.5.0 - Production
NLSRTL Version 10.2.0.5.0 - Production

I have a staff table with the columns staff_id and completion_date. The completion_date shows the date a staff member completed questionnaire. If the staff member did not complete the questionaire, then the completion_date column will be NULL.

Table Definition:

-- Create table
create table staff
(
staff_id number not null,
completion_date date
);

See attached text file (staff.sql) for Insert Statements.

The result set needs to have the following columns: ReportDate: the Sunday of each week. Completed: The number of staff who have completed the questionnaire by the ReportDate. NotCompleted: The number of staff who did not complete the questionnaire by the ReportDate. Total: The SUM of Completed and NotCompleted columns.

As the number of Completed goes up, the number of NotCompleted goes down. Eventually Completed will equal Total and NotCompleted goes to zero.

The result set would look similar as follows and used to generate a bar graph chart:

ReportDateCompletedNotCompletedTotal
2012-Apr-01814651473
2012-Apr-082214511473
2012-Apr-1514413291473
2012-Apr-2242010531473
2012-Apr-295788951473