your best bet is probably odbc, if you need to use navision functionality (codeuntis,...) then i would agree with kine, application server can do the job just fine, just make sure you read the manual cause you'll need to set messaging on the machine, application server and setup for messaging as well as learn how to call and what you get.
Besides that, I heard that odbc is quite slow. If you have an SQL database and plan to insert data to do something with it later, use table in navision as linked object. This allows you to create DTS packages for importing data from various databases (or even excel, text files, etc.) and then use that data directly from navision.
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Is it an SQL Database you can connect via ADO or anything else.
Regards
Another way is using Navision application server and comunicate through message queues.
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