Calculate the no of requests run per week

SELECT COUNT(*) Total, sum(decode(greatest(0,ceil (sysdate - actual_completion_date)), least(7,ceil(sysdate-actual_completion_date) ),1,0)) Week4, sum(decode(greatest(8,ceil (sysdate - actual_completion_date)), least(14,ceil(sysdate-actual_completion_date) ),1,0)) Week3, sum(decode(greatest(15,ceil (sysdate - actual_completion_date)), least(21,ceil(sysdate-actual_completion_date) ),1,0)) Week2, sum(decode(greatest(22,ceil (sysdate - actual_completion_date)), least(28,ceil(sysdate-actual_completion_date) ),1,0)) Week1 FROM FND_CONCURRENT_REQUESTS WHERE ACTUAL_COMPLETION_DATE is not null;