select year(getdate())
- year(DOB)
- case when month(DOB) > month(getdate()) then 1
when month(DOB) < month(getdate()) then 0
when day(DOB) > day(DOB) then 1
else 0
end as age
from Table
select year(getdate())
- year(DOB)
- case when month(DOB) > month(getdate()) then 1
when month(DOB) < month(getdate()) then 0
when day(DOB) > day(DOB) then 1
else 0
end as age
from Table