Calculating Age

select tech_id

,case

when DATEPART(DY, BIRTH_DATE) > DATEPART(DY, GETDATE())

then DATEDIFF(YYYY, BIRTH_DATE, GETDATE()) - 1

else DATEDIFF(YYYY, BIRTH_DATE, GETDATE())

end as AGE

from ST_TERM_DATA

The AGE field in the DataMart..StudentHistory table contains the age of the student at each census point in each term.