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914 lines
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data-chapter-title="Associations"
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<li class="chapter " data-level="0" data-path="./">
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<a href="./">
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Getting Started with GORM
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<li class="chapter " data-level="1" data-path="database.html">
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<b>1.</b>
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Database
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</a>
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<ul class="articles">
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<li class="chapter " data-level="1.1" data-path="database.html">
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<a href="database.html#connecting-to-a-database">
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<b>1.1.</b>
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Database Connection
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</a>
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<li class="chapter " data-level="1.2" data-path="database.html">
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<a href="database.html#migration">
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<b>1.2.</b>
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Migration
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="2" data-path="models.html">
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<a href="models.html">
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<b>2.</b>
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Models
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</a>
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<ul class="articles">
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<li class="chapter " data-level="2.1" data-path="models.html">
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<a href="models.html#model-definition">
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<b>2.1.</b>
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Model Definition
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</a>
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<a href="models.html#conventions">
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<b>2.2.</b>
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Conventions & Overriding
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</a>
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</li>
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<li class="chapter active" data-level="2.3" data-path="associations.html">
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<a href="associations.html">
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<b>2.3.</b>
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Associations
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</a>
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<ul class="articles">
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<li class="chapter " data-level="2.3.1" data-path="associations.html">
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<a href="associations.html#belongs-to">
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<b>2.3.1.</b>
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Belongs To
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</a>
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</li>
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<li class="chapter " data-level="2.3.2" data-path="associations.html">
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<a href="associations.html#has-one">
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<b>2.3.2.</b>
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Has One
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</a>
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</li>
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<li class="chapter " data-level="2.3.3" data-path="associations.html">
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<a href="associations.html#has-many">
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<b>2.3.3.</b>
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Has Many
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</a>
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</li>
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<li class="chapter " data-level="2.3.4" data-path="associations.html">
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<a href="associations.html#many-to-many">
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<b>2.3.4.</b>
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Many To Many
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</a>
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</li>
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<li class="chapter " data-level="2.3.5" data-path="associations.html">
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<a href="associations.html#polymorphism">
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<b>2.3.5.</b>
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Polymorphism
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</a>
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</li>
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<li class="chapter " data-level="2.3.6" data-path="associations.html">
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<a href="associations.html#association-mode">
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<b>2.3.6.</b>
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Association Mode
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</a>
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</li>
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</ul>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="3" data-path="curd.html">
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<a href="curd.html">
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<b>3.</b>
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CRUD: Reading and Writing Data
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</a>
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<ul class="articles">
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<li class="chapter " data-level="3.1" data-path="curd.html">
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<a href="curd.html#create">
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<b>3.1.</b>
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Create
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</a>
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</li>
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<li class="chapter " data-level="3.2" data-path="curd.html">
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<a href="curd.html#query">
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<b>3.2.</b>
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Query
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</a>
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</li>
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<li class="chapter " data-level="3.3" data-path="curd.html">
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<a href="curd.html#preloading-eager-loading">
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<b>3.3.</b>
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Preloading (Eager Loading)
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</a>
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</li>
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<li class="chapter " data-level="3.4" data-path="curd.html">
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<a href="curd.html#update">
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<b>3.4.</b>
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Update
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</a>
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</li>
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<li class="chapter " data-level="3.5" data-path="curd.html">
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<a href="curd.html#delete">
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<b>3.5.</b>
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Delete / Soft Delete
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="4" data-path="callbacks.html">
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<a href="callbacks.html">
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<b>4.</b>
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Callbacks
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</a>
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</li>
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<li class="chapter " data-level="5" data-path="advanced.html">
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<a href="advanced.html">
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<b>5.</b>
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Advanced Usage
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</a>
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<ul class="articles">
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<li class="chapter " data-level="5.1" data-path="advanced.html">
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<a href="advanced.html#error-handling">
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<b>5.1.</b>
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Error Handling
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</a>
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</li>
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<li class="chapter " data-level="5.2" data-path="advanced.html">
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<a href="advanced.html#transactions">
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<b>5.2.</b>
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Transactions
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</a>
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</li>
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<li class="chapter " data-level="5.3" data-path="advanced.html">
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<a href="advanced.html#sql-builder">
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<b>5.3.</b>
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Raw SQL & SQL Builder
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</a>
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</li>
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<li class="chapter " data-level="5.4" data-path="advanced.html">
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<a href="advanced.html#generic-database-interface-sqldb">
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<b>5.4.</b>
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Generic database interface sql.DB
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</a>
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</li>
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<li class="chapter " data-level="5.5" data-path="advanced.html">
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<a href="advanced.html#compose-primary-key">
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<b>5.5.</b>
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Composite Primary Key
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</a>
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</li>
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<li class="chapter " data-level="5.6" data-path="advanced.html">
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<a href="advanced.html#logger">
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<b>5.6.</b>
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Overriding Logger
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="6" data-path="development.html">
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<a href="development.html">
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<b>6.</b>
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Development
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</a>
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<ul class="articles">
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<li class="chapter " data-level="6.1" data-path="development.html">
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<a href="development.html#architecture">
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<b>6.1.</b>
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Architecture
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</a>
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</li>
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<li class="chapter " data-level="6.2" data-path="development.html">
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<a href="development.html#write-plugins">
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<b>6.2.</b>
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Write Plugins
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="7" data-path="changelog.html">
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<a href="changelog.html">
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<b>7.</b>
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Change Log
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</a>
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<!-- Title -->
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<h1>
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<i class="fa fa-circle-o-notch fa-spin"></i>
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<a href="." >Associations</a>
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</h1>
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<section class="normal markdown-section">
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<h1 id="associations">Associations</h1>
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<!-- toc -->
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<ul>
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<li><a href="#belongs-to">Belongs To</a></li>
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<li><a href="#has-one">Has One</a></li>
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<li><a href="#has-many">Has Many</a></li>
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<li><a href="#many-to-many">Many To Many</a></li>
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<li><a href="#polymorphism">Polymorphism</a></li>
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<li><a href="#association-mode">Association Mode</a></li>
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</ul>
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<!-- toc stop -->
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<h2 id="belongs-to">Belongs To</h2>
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<pre><code class="lang-go"><span class="hljs-comment">// `User` belongs to `Profile`, `ProfileID` is the foreign key</span>
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<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
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gorm.Model
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Profile Profile
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ProfileID <span class="hljs-keyword">int</span>
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}
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<span class="hljs-keyword">type</span> Profile <span class="hljs-keyword">struct</span> {
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gorm.Model
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Name <span class="hljs-keyword">string</span>
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}
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db.Model(&user).Related(&profile)
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<span class="hljs-comment">//// SELECT * FROM profiles WHERE id = 111; // 111 is user's foreign key ProfileID</span>
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</code></pre>
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<p><em>Specify Foreign Key</em></p>
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<pre><code class="lang-go"><span class="hljs-keyword">type</span> Profile <span class="hljs-keyword">struct</span> {
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gorm.Model
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Name <span class="hljs-keyword">string</span>
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}
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<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
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gorm.Model
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Profile Profile <span class="hljs-string">`gorm:"ForeignKey:ProfileRefer"`</span> <span class="hljs-comment">// use ProfileRefer as foreign key</span>
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ProfileRefer <span class="hljs-keyword">int</span>
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}
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</code></pre>
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<p><em>Specify Foreign Key & Association Key</em></p>
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<pre><code class="lang-go"><span class="hljs-keyword">type</span> Profile <span class="hljs-keyword">struct</span> {
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gorm.Model
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Refer <span class="hljs-keyword">string</span>
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Name <span class="hljs-keyword">string</span>
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}
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<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
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gorm.Model
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Profile Profile <span class="hljs-string">`gorm:"ForeignKey:ProfileID;AssociationForeignKey:Refer"`</span>
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ProfileID <span class="hljs-keyword">int</span>
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}
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</code></pre>
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<h2 id="has-one">Has One</h2>
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<pre><code class="lang-go"><span class="hljs-comment">// User has one CreditCard, UserID is the foreign key</span>
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<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
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gorm.Model
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CreditCard CreditCard
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}
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<span class="hljs-keyword">type</span> CreditCard <span class="hljs-keyword">struct</span> {
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gorm.Model
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UserID <span class="hljs-keyword">uint</span>
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Number <span class="hljs-keyword">string</span>
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}
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<span class="hljs-keyword">var</span> card CreditCard
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db.Model(&user).Related(&card, <span class="hljs-string">"CreditCard"</span>)
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<span class="hljs-comment">//// SELECT * FROM credit_cards WHERE user_id = 123; // 123 is user's primary key</span>
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<span class="hljs-comment">// CreditCard is user's field name, it means get user's CreditCard relations and fill it into variable card</span>
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<span class="hljs-comment">// If the field name is same as the variable's type name, like above example, it could be omitted, like:</span>
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db.Model(&user).Related(&card)
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</code></pre>
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<p><em>Specify Foreign Key</em></p>
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<pre><code class="lang-go"><span class="hljs-keyword">type</span> Profile <span class="hljs-keyword">struct</span> {
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gorm.Model
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Name <span class="hljs-keyword">string</span>
|
|
UserRefer <span class="hljs-keyword">uint</span>
|
|
}
|
|
|
|
<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Profile Profile <span class="hljs-string">`gorm:"ForeignKey:UserRefer"`</span>
|
|
}
|
|
</code></pre>
|
|
<p><em>Specify Foreign Key & Association Key</em></p>
|
|
<pre><code class="lang-go"><span class="hljs-keyword">type</span> Profile <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Name <span class="hljs-keyword">string</span>
|
|
UserID <span class="hljs-keyword">uint</span>
|
|
}
|
|
|
|
<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Refer <span class="hljs-keyword">string</span>
|
|
Profile Profile <span class="hljs-string">`gorm:"ForeignKey:UserID;AssociationForeignKey:Refer"`</span>
|
|
}
|
|
</code></pre>
|
|
<h2 id="has-many">Has Many</h2>
|
|
<pre><code class="lang-go"><span class="hljs-comment">// User has many emails, UserID is the foreign key</span>
|
|
<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Emails []Email
|
|
}
|
|
|
|
<span class="hljs-keyword">type</span> Email <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Email <span class="hljs-keyword">string</span>
|
|
UserID <span class="hljs-keyword">uint</span>
|
|
}
|
|
|
|
db.Model(&user).Related(&emails)
|
|
<span class="hljs-comment">//// SELECT * FROM emails WHERE user_id = 111; // 111 is user's primary key</span>
|
|
</code></pre>
|
|
<p><em>Specify Foreign Key</em></p>
|
|
<pre><code class="lang-go"><span class="hljs-keyword">type</span> Profile <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Name <span class="hljs-keyword">string</span>
|
|
UserRefer <span class="hljs-keyword">uint</span>
|
|
}
|
|
|
|
<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Profile []Profiles <span class="hljs-string">`gorm:"ForeignKey:UserRefer"`</span>
|
|
}
|
|
</code></pre>
|
|
<p><em>Specify Foreign Key & Association Key</em></p>
|
|
<pre><code class="lang-go"><span class="hljs-keyword">type</span> Profile <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Name <span class="hljs-keyword">string</span>
|
|
UserID <span class="hljs-keyword">uint</span>
|
|
}
|
|
|
|
<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Refer <span class="hljs-keyword">string</span>
|
|
Profile []Profiles <span class="hljs-string">`gorm:"ForeignKey:UserID;AssociationForeignKey:Refer"`</span>
|
|
}
|
|
</code></pre>
|
|
<h2 id="many-to-many">Many To Many</h2>
|
|
<pre><code class="lang-go"><span class="hljs-comment">// User has and belongs to many languages, use `user_languages` as join table</span>
|
|
<span class="hljs-keyword">type</span> User <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Languages []Language <span class="hljs-string">`gorm:"many2many:user_languages;"`</span>
|
|
}
|
|
|
|
<span class="hljs-keyword">type</span> Language <span class="hljs-keyword">struct</span> {
|
|
gorm.Model
|
|
Name <span class="hljs-keyword">string</span>
|
|
}
|
|
|
|
db.Model(&user).Related(&languages)
|
|
<span class="hljs-comment">//// SELECT * FROM "languages" INNER JOIN "user_languages" ON "user_languages"."language_id" = "languages"."id" WHERE "user_languages"."user_id" = 111</span>
|
|
</code></pre>
|
|
<p><em>Specify Foreign Key & Association Key</em></p>
|
|
<pre><code class="lang-go"><span class="hljs-keyword">type</span> CustomizePerson <span class="hljs-keyword">struct</span> {
|
|
IdPerson <span class="hljs-keyword">string</span> <span class="hljs-string">`gorm:"primary_key:true"`</span>
|
|
Accounts []CustomizeAccount <span class="hljs-string">`gorm:"many2many:PersonAccount;AssociationForeignKey:idAccount;ForeignKey:idPerson"`</span>
|
|
}
|
|
|
|
<span class="hljs-keyword">type</span> CustomizeAccount <span class="hljs-keyword">struct</span> {
|
|
IdAccount <span class="hljs-keyword">string</span> <span class="hljs-string">`gorm:"primary_key:true"`</span>
|
|
Name <span class="hljs-keyword">string</span>
|
|
}
|
|
</code></pre>
|
|
<h2 id="polymorphism">Polymorphism</h2>
|
|
<p>Supports polymorphic has-many and has-one associations.</p>
|
|
<pre><code class="lang-go"> <span class="hljs-keyword">type</span> Cat <span class="hljs-keyword">struct</span> {
|
|
Id <span class="hljs-keyword">int</span>
|
|
Name <span class="hljs-keyword">string</span>
|
|
Toy Toy <span class="hljs-string">`gorm:"polymorphic:Owner;"`</span>
|
|
}
|
|
|
|
<span class="hljs-keyword">type</span> Dog <span class="hljs-keyword">struct</span> {
|
|
Id <span class="hljs-keyword">int</span>
|
|
Name <span class="hljs-keyword">string</span>
|
|
Toy Toy <span class="hljs-string">`gorm:"polymorphic:Owner;"`</span>
|
|
}
|
|
|
|
<span class="hljs-keyword">type</span> Toy <span class="hljs-keyword">struct</span> {
|
|
Id <span class="hljs-keyword">int</span>
|
|
Name <span class="hljs-keyword">string</span>
|
|
OwnerId <span class="hljs-keyword">int</span>
|
|
OwnerType <span class="hljs-keyword">string</span>
|
|
}
|
|
</code></pre>
|
|
<p>Note: polymorphic belongs-to and many-to-many are explicitly NOT supported, and will throw errors.</p>
|
|
<h2 id="association-mode">Association Mode</h2>
|
|
<p>Association Mode contains some helper methods to handle relationship things easily.</p>
|
|
<pre><code class="lang-go"><span class="hljs-comment">// Start Association Mode</span>
|
|
<span class="hljs-keyword">var</span> user User
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>)
|
|
<span class="hljs-comment">// `user` is the source, it need to be a valid record (contains primary key)</span>
|
|
<span class="hljs-comment">// `Languages` is source's field name for a relationship.</span>
|
|
<span class="hljs-comment">// If those conditions not matched, will return an error, check it with:</span>
|
|
<span class="hljs-comment">// db.Model(&user).Association("Languages").Error</span>
|
|
|
|
|
|
<span class="hljs-comment">// Query - Find out all related associations</span>
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>).Find(&languages)
|
|
|
|
|
|
<span class="hljs-comment">// Append - Append new associations for many2many, has_many, will replace current association for has_one, belongs_to</span>
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>).Append([]Language{languageZH, languageEN})
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>).Append(Language{Name: <span class="hljs-string">"DE"</span>})
|
|
|
|
|
|
<span class="hljs-comment">// Delete - Remove relationship between source & passed arguments, won't delete those arguments</span>
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>).Delete([]Language{languageZH, languageEN})
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>).Delete(languageZH, languageEN)
|
|
|
|
|
|
<span class="hljs-comment">// Replace - Replace current associations with new one</span>
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>).Replace([]Language{languageZH, languageEN})
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>).Replace(Language{Name: <span class="hljs-string">"DE"</span>}, languageEN)
|
|
|
|
|
|
<span class="hljs-comment">// Count - Return the count of current associations</span>
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>).Count()
|
|
|
|
|
|
<span class="hljs-comment">// Clear - Remove relationship between source & current associations, won't delete those associations</span>
|
|
db.Model(&user).Association(<span class="hljs-string">"Languages"</span>).Clear()
|
|
</code></pre>
|
|
|
|
|
|
</section>
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