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66 lines
3.0 KiB
ReStructuredText
66 lines
3.0 KiB
ReStructuredText
Setting up GraphQL schema using an existing database
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====================================================
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When you have an existing database with a schema already present, you don't need to create tables or views or run
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DDL queries through the Hasura console.
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All you need to do is indicate to Hasura GraphQL engine which tables and views you want to expose over GraphQL and
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how they are connected to each other so that you can query them as a "graph".
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1) Track tables/views
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---------------------
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Tracking a table or a view means telling Hasura GraphQL engine that you want to expose that table/view over GraphQL.
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To track a table or a view:
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^^^^^^^^^^^^^^^^^^^^^^^^^^^
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#. Head to the ``Data -> Schema`` section of the console.
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#. Under the heading ``Untracked Tables/Views``, click on the ``Add`` button next to the table/view name.
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To track all tables and views present in the database:
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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#. Head to the ``Data -> Schema`` section of the console.
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#. Under the heading ``Untracked Tables/Views``, click the ``Add all`` button.
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2) Track foreign-keys
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---------------------
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Tracking a foreign-key means creating a :doc:`relationship <relationships/index>` between the tables involved in the
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foreign-key.
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To track a foreign-key between two tables in the database:
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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#. Head to the ``Data -> Schema`` section of the console.
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#. Click on a table involved in the foreign-key and head to the ``Relationships`` tab.
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#. You should see a suggested relationship based on the foreign-key. Click ``Add``, give a name to your relationship
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(this will be the name of the :doc:`nested object <../queries/nested-object-queries>` in the GraphQL query), and
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hit ``Save`` to create the relationship.
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#. Repeat with the other table involved in the foreign-key.
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To track all the foreign-keys of all tables in the database:
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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#. Head to the ``Data -> Schema`` section of the console.
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#. Under the heading ``Untracked Relations``, click on the ``Track Available Relations`` to automatically create
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relationships based on the foreign-keys.
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.. note::
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In this case, Hasura GraphQL engine will automatically generate relationship names (the names of the :doc:`nested
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objects <../queries/nested-object-queries>` in the GraphQL query) based on the table names and the foreign-key
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names. The name is generated in the following format:
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- For object relationships: ``Camel case of (foreignTableName + By + columnName)``
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- For array relationships: ``Camel case of (foreignTableName + s + By + columnNameInForeignTable)``
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For example, for the foreign-key ``article::author_id -> author::id``, the relationship names will be
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``authorByAuthorId`` for ``article`` table and ``articlesByAuthorId`` for ``author`` table.
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You can change the relationship names by heading to the ``Relationships`` tab of the concerned table and
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dropping and recreating the relationship with a name of your choice.
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