How would you set a condition in where clause in SQL Server? For example you have a parameter @ProjectID. If @ProjectID is 1, then select all employee with EmployeeNo 1000. If @ProjectID=2 then select all employee with employeeNo betweeen 1000 and 2000. SQL Case Statement might not work here so you will have to implment it otherwise. Try this query
Declare @ProjectID int
WHERE((@ProjectID=1 and EmployeeNo = 1000) OR (@ProjectID=0))
Hope it helps.