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75 lines
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ReStructuredText
75 lines
4.0 KiB
ReStructuredText
Relationships between tables/views
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==================================
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.. contents:: Table of contents
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:backlinks: none
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:depth: 1
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:local:
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To make :doc:`nested object queries <../../queries/nested-object-queries>`, the tables/views in your database need to
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be connected via relationships.
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Let's say we have the following tables in our database: ``author``, ``passport_info``, ``article`` and ``tag``.
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Table relationships
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-------------------
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The tables/views in any relational database are typically related to each other via one of the
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following types of table relationships:
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+------------------+-----------------------------------+------------------------------------------------+
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| Type | Example | Meaning |
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+==================+===================================+================================================+
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| ``one-to-one`` | ``author`` and ``passport_info`` | - an ``author`` can have one ``passport_info`` |
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| | | - a ``passport_info`` can have one ``owner`` |
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+------------------+-----------------------------------+------------------------------------------------+
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| ``one-to-many`` | ``author`` and ``article`` | - an ``author`` can have many ``articles`` |
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| | | - an ``article`` can have one ``author`` |
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+------------------+-----------------------------------+------------------------------------------------+
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| ``many-to-many`` | ``article`` and ``tag`` | - an ``article`` can have many ``tags`` |
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| | | - a ``tag`` can have many ``articles`` |
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+------------------+-----------------------------------+------------------------------------------------+
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GraphQL schema relationships
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----------------------------
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As you can see, each table relationship will have two component relationships (one in either direction) in the GraphQL
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schema. These relationships can be one of the following types:
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+-----------------------------------------+------------------------------------------+---------------------------------------------------------------------------------------+
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| Type | Example | Meaning |
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+=========================================+==========================================+=======================================================================================+
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| ``object relationship`` (one-to-one) | an ``article`` can have one ``author`` | an ``article`` object will have a single nested author object called ``author`` |
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+-----------------------------------------+------------------------------------------+---------------------------------------------------------------------------------------+
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| ``array relationship`` (one-to-many) | an ``author`` can have many ``articles`` | an ``author`` object will have an array of nested article objects called ``articles`` |
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+-----------------------------------------+------------------------------------------+---------------------------------------------------------------------------------------+
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.. note::
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The relationship name is used to refer to the nested objects in queries. For example, "``articles``" of an ``author``
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and "``author``" of an ``article``.
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Managing GraphQL relationships
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------------------------------
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See the following to manage the object/array relationships between tables/views for the GraphQL schema:
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- :doc:`create`
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- :doc:`rename`
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Table relationships modelling guides
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------------------------------------
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The following guides will help you model the different types of table relationships in the database:
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- :doc:`database-modelling/one-to-one`
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- :doc:`database-modelling/one-to-many`
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- :doc:`database-modelling/many-to-many`
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.. toctree::
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:maxdepth: 1
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:hidden:
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create
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rename
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Database modelling <database-modelling/index> |