Question

Rewording my original post for further clarification.

I current have the below tables:

Product_Ref

• product_id
• product_name

Products

• product_id
• so_date (date)
• total_sales

Calendar

• dt (date field, each row representing a single day for the past/next 10 years)

I am looking to produce a report that will tell me the number of products that were sold in the past 6 months (based on SYSDATE) on a daily basis, the report should be every combination of day in the last 6 months against every possible product_id in the format:

Product id | date | total sales

If I assume that there were 0 entries in the products table (i.e no sales) I would still expect a complete report output but instead it would show 6 months of zero’d data i.e.

1 | 2012-01-01 | 0
2 | 2012-01-01 | 0
3 | 2012-01-01 | 0
1 | 2012-01-02 | 0
2 | 2012-01-02 | 0
3 | 2012-01-02 | 0
…

This would assume there were 3 products in the product_reference table – my original query (noted below) was my starter for 10, but not sure where to go from here.

SELECT products.product_id, calendar.dt, products.total_sales
FROM products RIGHT JOIN calendar ON (products.so_date = calendar.dt)
WHERE calendar.dt < SYSDATE AND calendar.dt >= ADD_MONTHS(SYSDATE, -7)+1
ORDER BY calendar.dt ASC, products.product_id DESC;

Answer 1

The clue is in the question – you are looking for a CROSS JOIN.

SELECT products.product_id, calendar.dt, products.total_sales
FROM Product_Ref
CROSS JOIN calendar 
LEFT JOIN products ON products.so_date = calendar.dt 
                    AND products.product_id = Product_Ref.product_id
WHERE calendar.dt < SYSDATE AND calendar.dt >= ADD_MONTHS(SYSDATE, -7)+1
ORDER BY calendar.dt ASC, products.product_id DESC;

I was confused at first by your table names where “Product” in fact means “sale” and “Product_Ref” is a product!

This is very similar to an example of the use of CROSS JOIN I once posted here.