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Just like cursors on a primary database, you can use cursors on secondary databases to iterate over the records in a secondary database. Like cursors used with primary databases, you can also use cursors with secondary databases to search for specific records in a database, to seek to the first or last record in the database, to get the next duplicate record, and so forth. For a complete description on cursors and their capabilities, see Using Cursors.
However, when you use cursors with secondary databases:
Any data returned is the data contained on the primary database record referenced by the secondary record.
You cannot use DB_GET_BOTH and related flags with DB::c_get() and a secondary database. Instead, you must use DB::c_pget(). Also, in that case the primary and secondary key given on the call to DB::c_pget() must match the secondary key and associated primary record key in order for that primary record to be returned as a result of the call.
For example, suppose you are using the databases, classes, and key extractors described in Implementing Key Extractors . Then the following searches for a person's name in the secondary database, and deletes all secondary and primary records that use that name.
#include <db_cxx.h> ... Db my_database(NULL, 0); Db my_index(NULL, 0); // Get a cursor on the secondary database Dbc *cursorp; my_index.cursor(NULL, &cursorp, 0); // Name to delete char *search_name = "John Doe"; // Instantiate Dbts as normal Dbt key(search_name, strlen(search_name) + 1); Dbt data; // Position the cursor while (cursorp->get(&key, &data, DB_SET) == 0) cursorp->del(0);