Help needed in framing SQL query.

Question

Hi,
I have table having following schema:
PRODUCT_ID         INT
DATE                   DATETIME
ITEMS_SOLD         INT
This table contains data for a week (sunday to saturday). I want to write an SQL query to get (filter out) PRODUCT_ID of products which has same no. of ITEMS_SOLD for all 7 days. Also for given PRODUCT_ID I need to find the longest period of successive days where the no. of ITEMS_SOLD is same for all days in this period. Eg.(PRODUCT_ID 23 was sold as following along the week in no. of units sold: 4,6,6,6,6,7,4 .So the longest period is *4 days* from Monday to Thursday.) The first condition is special case of second condition where no. of days is 7.
Any help to get the SQL query will be appreciated.
Thanks,
Akshay.

Answer 1

PRODUCT_ID      DATE           ITEMS_SOLD
1          10/10/2011     3
1          11/10/2011     3
1          12/10/2011     3
1          13/10/2011     3
1           16/10/2011     5
2          10/10/2011     4
2           11/10/2011     4
2          12/10/2011     4
2          13/10/2011     4
2           14/10/2011     4
2          15/10/2011     4
2          16/10/2011     4
Output:
PRODUCT_ID ITEMS_SOLD NO_OF_DAYS
1          3                4     
2          4               7
Explanation of results:
The table to be queried contains data for 1 week: from 10/10/2011(Sunday) to 16/10/2011(Saturday). Now, product with PRODUCT_ID '1' was sold on dates 10,11,12,13,16. Out of these 5 days 3 units were sold on 4 successive days (from 10-13). So output should be like :
PRODUCT_ID ITEMS_SOLD NO_OF_DAYS
1          3               4     
as longest period of successive days is 4 where same no. of units were sold i.e 3 units (other period is of 1 day on 16th ).
For PRODUCT_ID 2 we have only one period of 7 days where 4 units were sold each day. So we output :
PRODUCT_ID ITEMS_SOLD NO_OF_DAYS
2           4               7
Other case where same PRODUCT_ID have different units sold on each day should be ignored.
I hope that clarifies the problem more. Let me know in case I have missed out anything which should have been mentioned.
-Akshay.