Question

I have a database table with the following structure –

Week_End      Sales 
2009-11-01    43223.43 
2009-11-08     4324.23 
2009-11-15    64343.23 
... 

What I want is a SQL statement that will take a start and end date, and identify all rows within that period where the sales figure is more than 3% above or below the average sales figure for that period. So, run against the above data, it would return –

Week_End       Sales 
2009-11-08     4324.23 

I am using SQL Server 2008, btw.

Answer 1

note: the average in your example is 37297, so all three values in the table end up being outside the tolerance.

;with Weeks as --narrows the range to the provided dates
(
    select * from YourTable 
    where Week_End between @StartDate and @EndDate
),
PercentOff as 
(
    select week_end, sales, abs((a.avg - sales)/a.avg) as pct
    from Weeks
    cross join (select avg(sales) as avg from Weeks) a
)
select * from PercentOff where pct >= .03