On Fri, 17 Oct 2008 07:53:52 +0000 (UTC), MikeW <[EMAIL PROTECTED]> wrote:
>John Belli <[EMAIL PROTECTED]> writes: >> >> On Thu, 16 Oct 2008 17:54:52 +0000 (UTC), MikeW >> <[EMAIL PROTECTED]> wrote: >> >> >My code has two pre-opened DB connection handles, and would like to >> >perform an SQL operation over the two databases. >> >The DB filenames are not available at this point, hence an ATTACH is >> >not feasible. >> >Is there any way to achieve this by applying an ATTACH at the handle level ? >> >> I don't think so, but check into "PRAGMA database_list" (See >> http://www.sqlite.org/pragma.html ). >> >> JAB > >Thanks, that might be useful in some situations but not in this one. > >The use case is a very specific one in which a database may contain one-off >overrides for a second, normally independent (but already opened) database. >I can obviously implement this by reading rows from the first one >and updating the second, but if I could briefly refer to both DBs at >the same time, it would be just one 'atomic' SQL statement - >much simpler and more robust. > >Still, it seems surprising that there isn't a (SQLite-specific) handle-level >operation to do this attach, maybe I should put in a feature request. >(Or even have a look in the SQLite code to see if it's an easy mod ...) GIVEN: db1 is the open handle of the first database, and db2 is the open handle of the second database WANTED: attach database open as db1 to db2 to do an atomic update * * * WARNING: untested code ahead! * * * char **table; sqlite3_get_table(db1, "PRAGMA database_list", &table, NULL, NULL, NULL); char *tmp = sqlite3_mprintf("ATTACH %q AS a", table[5]); sqlite3_free_table(table); sqlite3_exec(db2, tmp, NULL, NULL, NULL); sqlite3_free(tmp); ...do your stuff here... sqlite3_exec(db2, "DETACH a", NULL, NULL, NULL); There should be a bunch of error checking in there. This is left as an exercise for the reader. This will not work if db1 is a memory db. In that case, you would have to do it the other way around. If both are memory dbs, then you're out of luck. JAB -- John A. Belli Software Engineer Refrigerated Transport Electronics, Inc. http://www.rtelectronics.com _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
