Question

I know this should be painfully simple, but I’m having a mental block. I have three tables in a SQL Server 2008 database:

Users:

• ID
• Birthdate (datetime)

User_Visits:

• Site_ID
• User_ID
• Visit_Date

Sites:

• ID

I need a SQL statement that gets the count of sites that have visitors with an average age between say 40-50 years old.

Thanks in advance!

Answer 1

select count(*) as SiteCount
from (
      select avg(datediff(year, U.BirthDate, UV.Visit_Date)) as AvgAge
      from Users as U
        inner join User_Visits as UV
         on U.ID = UV.User_ID
      group by UV.Site_ID   
     ) as T
where AvgAge >= 40 and
      AvgAge < 50