Fix main explanation on views with joins (#537)
* Fix indentation and example view * Change films.id to just id
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@@ -1230,54 +1230,52 @@ It's also possible to embed `Materialized Views <https://www.postgresql.org/docs
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Embedding Views containing Joins
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Embedding Views containing Joins
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--------------------------------
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--------------------------------
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The same embedding rules applies to views with joined tables, that is, the column of any table participating in the join with a **foreign key** definition must be present in the view.
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On views that contain joins, PostgREST will infer the joined tables' foreign keys based on the sources of the view columns.
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For instance, let's create a view called ``film_competition_view`` that will join three tables:
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For instance, let's create a view called ``detailed_nominations_view`` that will join three tables:
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.. code-block:: postgres
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.. code-block:: postgres
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CREATE VIEW film_competition_view AS
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CREATE VIEW detailed_nominations_view AS
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SELECT
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SELECT
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films.title as film_title
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films.title as film_title
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, competitions.name as competition_name
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, competitions.name as competition_name
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, rank
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, film_id
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, film_id
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FROM
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FROM nominations
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nominations
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JOIN films ON films.id = nominations.film_id
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JOIN films ON films.id = nominations.film_id
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JOIN competitions ON competitions.id = nominations.competition_id;
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JOIN competitions ON competitions.id = nominations.competition_id;
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The view can be embedded with the table ``films`` because it has the ``film_id`` column from the ``nominations`` table, which has a relationship with ``films``.
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The view can be embedded with the table ``films`` because it has the ``film_id`` column from the ``nominations`` table, which has a relationship with ``films``.
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But what if you want to embed the view with the ``actors`` table? The ``film_id`` column alone will not allow it since it belongs to ``nominations``, which doesn't have a relationship to ``actors``. In this case, you need to select the ``films.id`` column from the ``films`` table, which has a many-to-many relationship with ``actors``.
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But what if you want to embed the view with the ``actors`` table? The ``film_id`` column alone will not allow it since it belongs to ``nominations``, which doesn't have a relationship to ``actors``. In this case, you need to select the ``id`` column from the ``films`` table, which has a many-to-many relationship with ``actors``.
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.. code-block:: postgres
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.. code-block:: postgres
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CREATE VIEW film_competition_view AS
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CREATE VIEW detailed_nominations_view AS
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SELECT
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SELECT
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films.title as film_title
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films.title as film_title
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, competitions.name as competition_name
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, competitions.name as competition_name
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, rank
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-- To keep the relationship with the films table, this column is renamed
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-- To keep the relationship with the films table, this column is renamed
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, film_id as nominations_film_id
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, film_id as nominations_film_id
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-- Adding this column allows the relationships we want
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-- Adding this column allows the relationships we want
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, films.id as film_id
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, films.id as film_id
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FROM
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FROM nominations
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nominations
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JOIN films ON films.id = nominations.film_id
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JOIN films ON films.id = nominations.film_id
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JOIN competitions ON competitions.id = nominations.competition_id;
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JOIN competitions ON competitions.id = nominations.competition_id;
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Now the view can embed both the ``films`` and ``actors`` tables:
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Now we can embed both the ``films`` and ``actors`` tables:
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.. tabs::
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.. tabs::
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.. code-tab:: http
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.. code-tab:: http
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GET /film_competition_view?select=film_title,films(language),actors(last_name,first_name)&competition_name=ilike.bafta HTTP/1.1
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GET /detailed_nominations_view?select=film_title,rank,films(language),actors(last_name,first_name)&competition_name=ilike.bafta HTTP/1.1
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.. code-tab:: bash Curl
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.. code-tab:: bash Curl
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curl "http://localhost:3000/film_competition_view?select=film_title,films(language),actors(last_name,first_name)&competition_name=ilike.bafta"
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curl "http://localhost:3000/detailed_nominations_view?select=film_title,rank,films(language),actors(last_name,first_name)&competition_name=ilike.bafta"
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As seen above, it is important to verify that the column in the view has the foreign key to the table you want to embed.
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.. _embedding_view_chains:
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.. _embedding_view_chains:
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