SQL query to compare product sales by month

Question

I have a Monthly Status database view I need to build a report based on. The data in the view looks something like this:

Category | Revenue  |  Yearh  |  Month
B         


        

Answer 1

The Case Statement is my best sql friend. You also need a table for time to generate your 0 rev in both months.

Assumptions are based on the availability of following tables:

sales: Category | Revenue | Yearh | Month

and

tm: Year | Month (populated with all dates required for reporting)

Example 1 without empty rows:

select
    Category
    ,month
    ,SUM(CASE WHEN YEAR = 2008 THEN Revenue ELSE 0 END) this_year
    ,SUM(CASE WHEN YEAR = 2007 THEN Revenue ELSE 0 END) last_year

from
    sales

where
    year in (2008,2007)

group by
    Category
    ,month

RETURNS:

Category  |  Month  |  Rev. This Year  |  Rev. Last Year
Bikes          1          10 000               0
Bikes          2          12 000               11 000
Bikes          3          12 000               11 500
Bikes          4          0                    15 400

Example 2 with empty rows: I am going to use a sub query (but others may not) and will return an empty row for every product and year month combo.

select
    fill.Category
    ,fill.month
    ,SUM(CASE WHEN YEAR = 2008 THEN Revenue ELSE 0 END) this_year
    ,SUM(CASE WHEN YEAR = 2007 THEN Revenue ELSE 0 END) last_year

from
    sales
    Right join (select distinct  --try out left, right and cross joins to test results.
                   product
                   ,year
                   ,month
               from
                  sales --this ideally would be from a products table
                  cross join tm
               where
                    year in (2008,2007)) fill


where
    fill.year in (2008,2007)

group by
    fill.Category
    ,fill.month

RETURNS:

Category  |  Month  |  Rev. This Year  |  Rev. Last Year
Bikes          1          10 000               0
Bikes          2          12 000               11 000
Bikes          3          12 000               11 500
Bikes          4          0                    15 400
Bikes          5          0                    0
Bikes          6          0                    0
Bikes          7          0                    0
Bikes          8          0                    0

Note that most reporting tools will do this crosstab or matrix functionality, and now that i think of it SQL Server 2005 has pivot syntax that will do this as well.

Here are some additional resources. CASE http://www.4guysfromrolla.com/webtech/102704-1.shtml SQL SERVER 2005 PIVOT http://msdn.microsoft.com/en-us/library/ms177410.aspx