Improve documentation.

doc/General.md

@@ -83,13 +83,13 @@ A prepared statement can also be removed with a call to `c->deallocate( name )`.
 
 The return value of `execute()` is of type `tao::pq::result`.
 
-For statements like `SELECT` or `UPDATE` the result can be used to query the number of affected or returned rows.
+For statements like `UPDATE` or `SELECT` the result contains the number of affected (or returned) rows.
 A complete list of statements for which this number is available can be found in the [PostgreSQL documentation](https://www.postgresql.org/docs/11/libpq-exec.html), see `PQcmdTuples()`.
 
 ```c++
 const auto r2 = tr->execute( "DeleteUser", 42 );
 assert( r2.has_affected_rows() );
-std::cout << r2.affected_rows() << std::endl;
+const std::size_t ar = r2.affected_rows();
 ```
 
 For all other statements, nothing useful can be done with the result.