How to calculate age (in years) based on Date of Birth and getDate()

Question

I have a table listing people along with their date of birth (currently a nvarchar(25))

How can I convert that to a date, and then calculate their age in years?

Answer 1

Here is how i calculate age given a birth date and current date.

select case 
            when cast(getdate() as date) = cast(dateadd(year, (datediff(year, '1996-09-09', getdate())), '1996-09-09') as date)
                then dateDiff(yyyy,'1996-09-09',dateadd(year, 0, getdate()))
            else dateDiff(yyyy,'1996-09-09',dateadd(year, -1, getdate()))
        end as MemberAge
go