You don't specify a data type when creating a computed column. The data type depends on the result of the expression.
Create table #Test (
emp_id int,
emp_Birth_Date DATETIME,
emp_Age AS datediff(d,emp_Birth_Date, getdate())
)
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability