pg: Add a few result fetching methods

I'm not sure if these are free from memory leaks, need to find a way to
test for that.

FU/PG.pm

@@ -108,7 +108,8 @@ used.
 
 =back
 
-Statement objects returned by C<< $conn->q() >> support the following methods:
+Statement objects returned by C<< $conn->q() >> can be inspected with the
+following two methods:
 
 =over
 
@@ -137,6 +138,40 @@ returns.
   #   { name => 'title', oid => 25 },
   # ]
 
+
+=back
+
+The statement can be executed with one of the following methods, depending on
+how you'd like to obtain the results:
+
+=over
+
+=item B<< $st->exec >>
+
+Execute the query and return the number of rows affected. Similar to C<<
+$conn->exec >>.
+
+=item B<< $st->val >>
+
+Return the first column of the first row. Throws an error if the query does not
+return exactly one column, or if multiple rows are returned. Returns I<undef>
+if no rows are returned or if its value is I<NULL>.
+
+=item B<< $st->rowl >>
+
+Return the first row as a list. Throws an error if the query does not return
+exactly one row.
+
+=item B<< $st->rowa >>
+
+Return the first row as an arrayref, equivalent to C<< [$st->rowl] >> but
+probably slightly more efficient.
+
+=item B<< $st->rowh >>
+
+Return the first row as a hashref. Also throws an error if the query returns
+multiple columns with the same name.
+
 =back
 
 =head2 Transactions
@@ -194,4 +229,9 @@ A thin wrapper around libpq. Lacks many higher-level conveniences and does not
 support binary transfers (at the time of writing, but then again there's little
 benefit in dealing with the binary format in pure perl anyway).
 
+=item L<DBIx::Simple>
+
+A popular DBI wrapper with some API conveniences. I may have taken some
+inspiration from it in the design of this module's API.
+
 =back