Question

There is a result set where all the records are unique columns like this .
I only want to display the records with newer dates if there is another record which belongs to the same BusinessID.
My query to get this result is

SELECT 
  FirstName, 
  LastName,
  Department,
  StartDate,
  Title,
  PhoneNumber,
  BusinessEntityID
FROM
  (SELECT
     E.BusinessEntityID,
     H.FirstName,
     H.LastName,
     H.Title,
     H.Department,
     E.PhoneNumber,
     E.CountryRegionName,
     E.PostalCode,
     H.StartDate
   FROM 
     CS120Exam_EmployeeDepartmentHistory H
   JOIN 
     CS120Exam_Employee E
   ON 
     E.BusinessEntityID=H.BusinessEntityID ) x 
   ORDER BY BusinessEntityID

And the result is

BusinessID  FirstName LastName Department StartDate
----------- --------- -------- ---------- ----------
1           aaa       mate     staff      2002-02-02 <----- DO NOT want this 
1           aaa       mate     admin      2004-03-05
2           john      mate     admin      2001-03-06
3           sun       kent     admin      2004-03-05
4           bbb       clark    staff      2006-02-02 <----- DO NOT want this 
4           bbb       clark    admin      2009-03-05

Answer 1

You need a sub-select to find the latest date for each BusinessEntityID. Try this (untested, of course):

SELECT 
  FirstName, 
  LastName,
  Department,
  StartDate,
  Title,
  PhoneNumber,
  BusinessEntityID
FROM
  (SELECT
     E.BusinessEntityID,
     H.FirstName,
     H.LastName,
     H.Title,
     H.Department,
     E.PhoneNumber,
     E.CountryRegionName,
     E.PostalCode,
     H.StartDate
   FROM 
     CS120Exam_EmployeeDepartmentHistory H
   JOIN 
     CS120Exam_Employee E
   ON 
     E.BusinessEntityID=H.BusinessEntityID ) x 
   WHERE x.StartDate = 
     (SELECT 
        Max(cs.StartDate) 
      FROM
        CS120Exam_EmployeeDepartmentHistory cs
      WHERE
        cs.BusinessEntityID = x.BusinessEntityID)
   ORDER BY BusinessEntityID