Add an example of select(update()) to the docs (#838)

docs/update.rst

@@ -41,6 +41,23 @@ You can conditionally update a property by using an :ref:`optional parameter
     }))
   );
 
+Note that ``e.update`` will return just the ``{ id: true }`` of the updated object. If you want to select further properties, you can wrap the update in a ``e.select`` call. This is still just a single query to the database.
+
+.. code-block:: typescript
+
+  e.params({ id: e.uuid, title: e.optional(e.str) }, (params) => {
+    const updated = e.update(e.Movie, (movie) => ({
+      filter_single: { id: params.id },
+      set: {
+        title: e.op(params.title, "??", movie.title),
+      },
+    }));
+    return e.select(updated, (movie) => ({
+      title: movie.title,
+    }));
+  });
+
+
 
 Updating links
 ^^^^^^^^^^^^^^