Oracle query on dblinked SQL Server tables returns ORA-00904 error

Question

Hi,
I have created a dblink to a SQL Server database from Oracle using Generic Connectivity.
The following query returns ORA-00904 Invalid Identifier error in the WHERE clause (tblEmp.Empno)
SELECT "EmpNo","EmpName", "DeptName"
FROM tblEmp@sqlserver,
tblDept@sqlserver
WHERE tblDept.DeptNo = tblEmp.Empno
I had to enclose the column names in double quotes due to case sensitivitiy of the columns, but I can't do the
same for the WHERE clause.
1) So, how do I fix this error ?
2) Also how do I include Deptno column with table alias in the columns list?
(Deptno is ambiguous in Emp and Dept tables)
Regards,
Sam

Answer 1

Alex
Because using the aliases all the time can become annoying and lead to disparate standards when used by multiple developers. For a one-off query I would go with aliases in the query but if the linked tables are going to be interrogated extensively I would prefer to create vanilla views of the underlying tables so that the aliases aren't necessary.
Just my opinion, it feels a bit cleaner to do it this way - you only do the work once in creating the view and then you don't need to worry about the case sensitivity of the linked database. You can also refer to the source in the name of the view so you don't have to think about different source databases with the same table names.
Cheers
Ben