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The func_odbc dialplan function is arguably the coolest and most powerful dialplan function in Asterisk. It allows you to create and use fairly simple dialplan functions that retrieve and use information from databases directly in the dialplan. There are all kinds of ways in which this might be used, such as for managing users or allowing the sharing of dynamic information within a clustered set of Asterisk machines.
What func_odbc allows you to do is define SQL queries to which you assign function names. In effect, you are creating custom functions that obtain their results by executing queries against a database. The func_odbc.conf file is where you specify the relationships between the function names you create and the SQL statements you wish them to perform. By referring to the named functions in the dialplan, you can retrieve and update values in the database.