[docs] sqlalchemy basics and api ref.

docs/extension/sqlalchemy.rst

@@ -16,19 +16,57 @@ To install the extension, use the `sqlalchemy` extra:
 
 .. note:: You can install more than one extra at a time separating the names with commas.
 
-Overview
-::::::::
+Overview and examples
+:::::::::::::::::::::
 
 There are two main tools provided by this extension. One reader, one writer.
 
+Let's select some data:
+
+.. code-block:: python
+
+    import bonobo
+    import bonobo_sqlalchemy
+
+    def get_graph():
+        graph = bonobo.Graph()
+        graph.add_chain(
+            bonobo_sqlalchemy.Select('SELECT * FROM example', limit=100),
+            bonobo.PrettyPrinter(),
+        )
+
+And let's insert some data:
+
+.. code-block:: python
+
+    import bonobo
+    import bonobo_sqlalchemy
+
+
+    def get_graph(**options):
+        graph = bonobo.Graph()
+        graph.add_chain(
+            ...,
+            bonobo_sqlalchemy.InsertOrUpdate('example')
+        )
+
+        return graph
 
-Details
-:::::::
 
 Reference
 :::::::::
 
+.. module:: bonobo_sqlalchemy
 
+Select
+------
+
+.. autoclass:: Select
+
+InsertOrUpdate
+--------------
+
+.. autoclass:: InsertOrUpdate
 
 Source code
 :::::::::::