C/C++ interface

Hello,

in the C interface documentation there is an example using:
   res = PQexec(conn, "DECLARE mycursor CURSOR FOR select * from
pg_database");   if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)   {       fprintf(stderr, "DECLARE CURSOR command
failed\n");      PQclear(res);       exit_nicely(conn);   }   PQclear(res);   res = PQexec(conn, "FETCH ALL in
mycursor");

...etc. So the statements are:

DECLARE mycursor CURSOR FOR select * from pg_database;
FETCH ALL in mycursor;

What's the difference between this and simply doing:
select * from pg_database;

I tried this in psql, the result seemed the same.

What I'm really using, however, is the C++ interface.
Its documentation is not yet complete.
There, too, I tried a version with and without cursor.
The result seems to be the same, but returned int is always 0
for the version without cursor, so I get no information whether
the query succeeded. 

Is someone maintaining the C++ interface and its documentation?


Thanks,

Volker Paul