SQL query for various time periods - mysql

Question

I have a table that contains Following entries:
completed_time|| BOOK_CNT
*********************************************
2013-07-23 | 2
2013-07-22 | 1
2013-07-19 | 3
2013-07 16 |5
2013-07-12 |4
2013-07-11 |2
2013-07-02 |9
2013-06-30 |5
Now, I want to use above entries for data analysis.
Lets say DAYS_FROM, DAYS_TO and PERIOD are three variables.
I need to fire following sort of queries:
"Total book from DAYS_FROM to DAYS_TO in interval of PERIOD."
DAYS_FROM is a date in format YYYY-MM-DD
,DAYS_TO is a date in format YYYY-MM-DD
PERIOD is {1W,2W,1M,2M,1Y}
where W,M,Y represents WEEK,MONTH and YEAR.
Example: The queries DAYS_FROM=2013-07-23 , DAYS_TO=2013-07-03 and PERIOD=1W should return:
ith week - total
1 - 3
2- 8
3- 6
4- 14
Explanation:
1-3 means (The total book from 2013-07-21(sun) to 2013-07-23(tue) is 3 )
2-8 means (The total book from 2013-07-14(sun) to 2013-07-21(sun) is 8 )
3-16 means (The total book from 2013-07-07(sun) to 2013-07-14(sun) is 6 )
4-14 means (The total book from 2013-07-03(wed) to 2013-07-07(sun) is 14 )
Please refer the calendar image for better understanding.
How to fire such query?
What I tried?
SELECT DAY(completed_time), COUNT(total) AS Total
FROM my_tab
WHERE completed_time BETWEEN '2013-07-23' - INTERVAL 1 WEEK AND '2013-07-03'
GROUP BY DAY(completed_time);
The above queries subtracted 7 days from 2013-07-23 and thus considered 2013-07-16 to 2013-07-23 as first week, 2013-07-09 to 2013-07-16 as second week and so on.

Answer 1

A simple starting point would be something like below, of course you may want to adjust the ith value to suit your needs;
SET #period='1M';
SELECT CASE WHEN #period='1Y' THEN YEAR(completed_time)
WHEN #period='1M' THEN YEAR(completed_time)*100+MONTH(completed_time)
WHEN #period='2M' THEN FLOOR((YEAR(completed_time)*100+MONTH(completed_time))/2)*2
WHEN #period='1W' THEN YEARWEEK(completed_time)
WHEN #period='2W' THEN FLOOR(YEARWEEK(completed_time)/2)*2
END ith,
SUM(BOOK_CNT) Total
FROM my_tab
GROUP BY ith
ORDER BY ith DESC;
An SQLfiddle to test with.