Suppose you have defined the following external authorization object:
CREATE AUTHORIZATION DEFINER sales USER 'salesdept' PASSWORD 'secret';
You now create the following C UDF:
CREATE FUNCTION sales_collect ( store_number INTEGER, item_no INTEGER) RETURNS INTEGER LANGUAGE C NO SQL EXTERNAL 'cs!salecol!salecollector.c' PARAMETER STYLE SQL EXTERNAL SECURITY DEFINER sales;
This function collects data associated with sales for a given store for a given item number (item_no) and returns the number of items sold. One possible, albeit contrived, scenario would have the function communicating with the store via a network interface. The function is created using the DEFINER context. This means that when a user logs onto its database account and executes an SQL request that invokes this function, it uses the logon ID associated with the sales authorization object, not the user that is executing the invoking SQL request. In this example, OS user salesdept has access to the external data the function reads to obtain the information it needs.