MSDAORA Oracle upgrade connectivity Problem

Oracle client always have connectivity problem to the Oracle database server due to the improper configuration in C:\Oracle\Ora81\network\ADMIN\TNSNAMES.ORA (Assume you did not change the default install folder)

Sometimes you may experience all the configuration are fine, you also can use TNSPING and SQLPLUS to access the ORACLE server without problem, but your Application using MSDAORA provider is facing problem to access the Oracle Server, you may get the error like:-
Error while trying to retrieve text for error ORA-03121
This is usually happen after you upgraded your Oracle client, you have restarted your machine, all the TNSNAMES.ORA entries are correct, everything is fine except your application, either ASP, ASP.NET, VB.NET or any application that use MSDAORA provider.
Why the problem happen is, after you upgraded your Oracle client, your MSDAORA still pointing to the old Oracle version, that's why the problem occurs.
To resolve this problem, goto your machine MSDAORA home C:\Program Files\Common Files\System\Ole DB folder, you will see there are some .reg files:-
mtxoci81_winnt.reg
mtxoci81_win2k.reg
mtxoci7x_winnt.reg
mtxoci7x_win2k.reg
If your Oracle client is 8.1 with Windows 2000 and above, double click the mtxoci81_win2k.reg file to register the new registry for the newer client. Then restart your machine, the problem will be solved automatically.
The content of the mtxoci81_win2k.reg is
REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSDTC\MTxOCI]
"OracleXaLib"="oraclient8.dll"
"OracleSqlLib"="orasql8.dll"
"OracleOciLib"="oci.dll"
The nice thing about Oracle is, once the Oracle problem is resolved, you will enjoy with Oracle.

ADO filter with NULL value

NULL value in database means no storage in the cell, if you use ADO to query the data and you would like to filter the NULL value, it will be a challenge for a lot of programmers.

Let's see the following code:-

dim rs, strSQL
strSQL = "SELECT EmployeeId, ReportsTo FROM Employees"
Set rs = CreateObject("ADODB.Recordset")
rs.cursorlocation = 3 ' -- adUseClient
rs.Open strSQL, connobj ' -- Assume the connobj already has open connection
do while not rs.eof
rs.movenext
loop
rs.close

The code above is retreiving data from MS SQL Server Northwind database, it tries to get the employeeId and superior employee Id (reportsTo column).

Let's say the requirement is those employee without superior display in one panel and those employee with superior display in another panel.

I believe no one want to query the database two times by using SQL query "SELECT EmployeeId, ReportsTo From Employees WHERE ReportsTo IS NULL" and "SELECT EmployeeId, ReportsTo From Employees WHERE ReportsTo IS NOT NULL", so we will query one time from the database by re-using the above code.

You will add another code before the while loop:-
rs.filter = "ReportsTo IS NULL"

Immediately you will get this error:-
Arguments are of the wrong type, are out of acceptable range, or are in conflict with one another

The reason being is because ADO Filter does not support "IS" and "NULL" statement, even you tried to use the filter as ISNULL(ReportsTo, 'N/A') = 'N/A' also get the same problem.

The only solution to this is back to the SQL query, change the query as
SELECT EmployeeId, ISNULL(ReportsTo, 'N/A') FROM Employees

Then the rs.filter use ReportsTo = 'N/A' will solve the problem, the whole code is shown below:-

dim rs, strSQL
strSQL = "SELECT EmployeeId, ISNULL(ReportsTo, 'N/A') FROM Employees"
Set rs = CreateObject("ADODB.Recordset")
rs.cursorlocation = 3 ' -- adUseClient
rs.Open strSQL, connobj ' -- Assume the connobj already has open connection
rs.Filter = "ReportsTo = 'N/A'"
do while not rs.eof
' -- Display Data in Superior Panel
rs.movenext
loop
rs.Filter = "ReportsTo <> 'N/A'"
do while not rs.eof
' -- Display Data in Subordinate Panel
rs.movenext
loop
rs.close



Cheers!