SQL query to compare product sales by month
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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
Bikes 10 000 2008 1
Bikes 12 000 2008 2
Bikes 12 000 2008 3
Bikes 15 000 2008 1
Bikes 11 000 2007 2
Bikes 11 500 2007 3
Bikes 15 400 2007 4
... And so forth
The view has a product category, a revenue, a year and a month. I want to create a report comparing 2007 and 2008, showing 0 for the months with no sales. So the report should look something like this:
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
The key thing to notice is how month 1 only has sales in 2008, and therefore is 0 for 2007. Also, month 4 only has no sales in 2008, hence the 0, while it has sales in 2007 and still show up.
Also, the report is actually for financial year - so I would love to have empty columns with 0 in both if there was no sales in say month 5 for either 2007 or 2008.
The query I got looks something like this:
SELECT
SP1.Program,
SP1.Year,
SP1.Month,
SP1.TotalRevenue,
IsNull(SP2.TotalRevenue, 0) AS LastYearTotalRevenue
FROM PVMonthlyStatusReport AS SP1
LEFT OUTER JOIN PVMonthlyStatusReport AS SP2 ON
SP1.Program = SP2.Program AND
SP2.Year = SP1.Year - 1 AND
SP1.Month = SP2.Month
WHERE
SP1.Program = 'Bikes' AND
SP1.Category = @Category AND
(SP1.Year >= @FinancialYear AND SP1.Year <= @FinancialYear + 1) AND
((SP1.Year = @FinancialYear AND SP1.Month > 6) OR
(SP1.Year = @FinancialYear + 1 AND SP1.Month <= 6))
ORDER BY SP1.Year, SP1.Month
The problem with this query is that it would not return the fourth row in my example data above, since we didn't have any sales in 2008, but we actually did in 2007.
This is probably a common query/problem, but my SQL is rusty after doing front-end development for so long. Any help is greatly appreciated!
Oh, btw, I'm using SQL 2005 for this query so if there are any helpful new features that might help me let me know.
Answer |
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