Import partial table from remote DB into a local microsoft access DB - sql

Question

Problem:
I'm trying to import a portion of a table from a remote informix db into an access 2016 database. The table to be partially imported contains account information and is > 2 GB (which as I understand it is the max size of a access db).
I only need information for the last year which is much less than 2 GB but the information must be updated at the end of each day.
Two solutions I have seen online are:
(A) Link the tables:
I'm reluctant to do this for two reasons:
1) I don't want additional load placed on the server everytime the enduser of the access db runs a report.
2) I don't want any changes carried out in the access DB to carry over to the live informix DB (this is absolutely cruical)
(B) Copy over the entire table via the access GUI
I don't think this is a viable solution for the following reasons:
1) The table is over 2GB
2) Reports must be ran on the table everyday with daily updated information. This would require pulling the entire informix table into access everyday.
Work So far:
I have succefully connected to the informix db from access via creating a dsn for the informix db.
I have also sucessfully imported a smaller table from the informix server via VBA with the following code:
DoCmd.TransferDatabase acImport, "ODBC Database", "ODBC;DSN=My_DSN_Name;UID=odbc;PWD=My_PWD;LANGUAGE=us_english;" & "DATABASE = My_DB_Name", acTable, "My_Destination_Tbl_Name", "TestTableImport", False, True
My ideal solution would see the enduser of the access db press a button that updates the local access copy of the db with all changes made to the informix db since the last update.
I have limited experience with access and VBA so would really appreciate any pointers on how I should proceed. Perhaps I have overlooked something simple?
Thanks for reading and any advice you can provide,
John

Answer 1

Ummmm.... assuming the data in the table is static (no updates to column data, just new rows) you could do something like importing whatever subset of data you want in Access and then every time you click a button run a macro to check what is the latest row in the access table.
Use that info to select only new rows from the ODBC source and insert them in the access table.
I tried this with Access 2013:
Sub test()
Dim cnDB As New ADODB.Connection
Dim rsRecords As New ADODB.Recordset
' find last row
Set db = CurrentDb
strSQL = "SELECT TOP 1 empno As lastemp FROM informix_employee ORDER BY empno DESC"
Set rs = db.OpenRecordset(strSQL, dbOpenSnapshot)
lastemp = rs("lastemp")
rs.Close
' get new rows from odbc source
DoCmd.SetWarnings False
cnDB.Open "DSN=ids1210;uid=informix;pwd=password"
rsRecords.Open "Select * from employee where empno>" & lastemp, cnDB
Do While Not rsRecords.EOF
strNaam = rsRecords.Fields(0).Value
rsRecords.MoveNext
' update access table
DoCmd.RunSQL ("insert into informix_employee (empno) values ('" + strNaam + "')")
Loop
rsRecords.Close
Set rsRecords = Nothing
cnDB.Close
Set cnDB = Nothing
db.Close
End Sub
It's a basic example, but should give you an idea of how to do it.
The code above inserts only one column per row (empno), you will need go through your table and do the insert with all the columns (basically create the insert ............. statement for your table)
'informix_employee' is the Access table.
'employee' is the Informix table.
Also, you need to reference ADO, e.g. 'Microsoft ActiveX Data Objects 6.1' to get it working, otherwise it will fail as the ADODB object wont be there.
If the Informix table does get some column updates (not just new rows) it would be quite difficult, as nothing (IDS/ODBC/Access) will be able to tell you which rows were updated without getting the data and comparing it with the previous set.