How do I do that in Oledb? Well, creating separate command objects with the SQL is easy and running the command is easy, but how do you join them and have one build on the previous result, which will be a datatable, I believe. Or a Reader.
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>TIA
Yes, it can be either a datatable or a reader.
There are several ways to join them. The best way will depend on the specifics of your data.
The simplest way is to create the final datatable and do for loops that scan the interim datatables and fill up the final datatable.
There are slicker, more elegant methods using LINQ or the one referenced below, but the for loops have always worked for me.
http://support.microsoft.com/kb/326080/en-us

As your conversion project evolves, you might find yourself having to merge .DBF data with data from MSSQL or MySQL.
The for loops are a good way to do that.