/*Старейший сотрудник*/
select e1.*
from DimEmployee as e1 
where e1.BirthDate = (select min(e2.BirthDate) from DimEmployee as e2)

/*Старейшая сотрудница*/
select *
from DimEmployee
where Gender='F' AND BirthDate = (select min(BirthDate) from DimEmployee where Gender='F')