787 lines
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787 lines
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data-chapter-title="Advanced Usage"
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data-revision="Fri Feb 26 2016 21:50:14 GMT+0800 (CST)"
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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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</a>
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</li>
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<li class="chapter " data-level="1" data-path="database.html">
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<a href="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>
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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 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-defination">
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<b>2.1.</b>
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Model Defination
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</a>
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</li>
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<li class="chapter " data-level="2.2" data-path="models.html">
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<a href="models.html#conventions-overriding-conventions">
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<b>2.2.</b>
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Naming Conventions & Overriding
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</a>
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</li>
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<li class="chapter " 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 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">
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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 active" 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#compose-primary-key">
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<b>5.4.</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="5.5" data-path="advanced.html">
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<a href="advanced.html#logger">
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<b>5.5.</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#callbacks">
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<b>6.1.</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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<!-- 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="" >Advanced Usage</a>
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</h1>
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<section class="normal markdown-section">
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<h1 id="advanced-usage">Advanced Usage</h1>
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<!-- toc -->
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<ul>
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<li><a href="#error-handling">Error Handling</a></li>
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<li><a href="#transactions">Transactions</a><ul>
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<li><a href="#a-specific-example">A Specific Example</a></li>
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</ul>
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</li>
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<li><a href="#raw-sql">Raw SQL</a></li>
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<li><a href="#row-rows">Row & Rows</a><ul>
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<li><a href="#scan-rows">Scan Rows</a></li>
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</ul>
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</li>
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<li><a href="#composite-primary-key">Composite Primary Key</a></li>
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<li><a href="#logger">Logger</a><ul>
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<li><a href="#customize-logger">Customize Logger</a></li>
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</ul>
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</li>
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</ul>
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<!-- toc stop -->
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<h2 id="error-handling">Error Handling</h2>
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<pre><code class="lang-go">query <span class="token operator">:=</span> db<span class="token operator">.</span><span class="token function">Where<span class="token punctuation">(</span></span><span class="token string">"name = ?"</span><span class="token operator">,</span> <span class="token string">"jinzhu"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">First<span class="token punctuation">(</span></span><span class="token operator">&</span>user<span class="token operator">)</span>
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query <span class="token operator">:=</span> db<span class="token operator">.</span><span class="token function">First<span class="token punctuation">(</span></span><span class="token operator">&</span>user<span class="token operator">)</span><span class="token operator">.</span><span class="token function">Limit<span class="token punctuation">(</span></span><span class="token number">10</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Find<span class="token punctuation">(</span></span><span class="token operator">&</span>users<span class="token operator">)</span>
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<span class="token comment" spellcheck="true">// query.Error will return the last happened error</span>
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<span class="token comment" spellcheck="true">// So you could do error handing in your application like this:</span>
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<span class="token keyword">if</span> err <span class="token operator">:=</span> db<span class="token operator">.</span><span class="token function">Where<span class="token punctuation">(</span></span><span class="token string">"name = ?"</span><span class="token operator">,</span> <span class="token string">"jinzhu"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">First<span class="token punctuation">(</span></span><span class="token operator">&</span>user<span class="token operator">)</span><span class="token operator">.</span>Error<span class="token operator">;</span> err <span class="token operator">!=</span> <span class="token boolean">nil</span> <span class="token operator">{</span>
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<span class="token comment" spellcheck="true">// error handling...</span>
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<span class="token operator">}</span>
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<span class="token comment" spellcheck="true">// RecordNotFound</span>
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<span class="token comment" spellcheck="true">// If no record found when you query data, gorm will return RecordNotFound error, you could check it like this:</span>
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db<span class="token operator">.</span><span class="token function">Where<span class="token punctuation">(</span></span><span class="token string">"name = ?"</span><span class="token operator">,</span> <span class="token string">"hello world"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">First<span class="token punctuation">(</span></span><span class="token operator">&</span>User<span class="token operator">{</span><span class="token operator">}</span><span class="token operator">)</span><span class="token operator">.</span>Error <span class="token operator">==</span> gorm<span class="token operator">.</span>RecordNotFound
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<span class="token comment" spellcheck="true">// Or use the shortcut method</span>
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db<span class="token operator">.</span><span class="token function">Where<span class="token punctuation">(</span></span><span class="token string">"name = ?"</span><span class="token operator">,</span> <span class="token string">"hello world"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">First<span class="token punctuation">(</span></span><span class="token operator">&</span>user<span class="token operator">)</span><span class="token operator">.</span><span class="token function">RecordNotFound<span class="token punctuation">(</span></span><span class="token operator">)</span>
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<span class="token keyword">if</span> db<span class="token operator">.</span><span class="token function">Model<span class="token punctuation">(</span></span><span class="token operator">&</span>user<span class="token operator">)</span><span class="token operator">.</span><span class="token function">Related<span class="token punctuation">(</span></span><span class="token operator">&</span>credit_card<span class="token operator">)</span><span class="token operator">.</span><span class="token function">RecordNotFound<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token operator">{</span>
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<span class="token comment" spellcheck="true">// no credit card found error handling</span>
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<span class="token operator">}</span>
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</code></pre>
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<h2 id="transactions">Transactions</h2>
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<p>To perform a set of operations within a transaction, the general flow is as below.
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The database handle returned from <code>db.Begin()</code> should be used for all operations within the transaction.
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(Note that all individual save and delete operations are run in a transaction by default.)</p>
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<pre><code class="lang-go"><span class="token comment" spellcheck="true">// begin</span>
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tx <span class="token operator">:=</span> db<span class="token operator">.</span><span class="token function">Begin<span class="token punctuation">(</span></span><span class="token operator">)</span>
|
|
|
|
<span class="token comment" spellcheck="true">// do some database operations (use 'tx' from this point, not 'db')</span>
|
|
tx<span class="token operator">.</span><span class="token function">Create<span class="token punctuation">(</span></span><span class="token operator">...</span><span class="token operator">)</span>
|
|
<span class="token operator">...</span>
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|
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<span class="token comment" spellcheck="true">// rollback in case of error</span>
|
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tx<span class="token operator">.</span><span class="token function">Rollback<span class="token punctuation">(</span></span><span class="token operator">)</span>
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|
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<span class="token comment" spellcheck="true">// Or commit if all is ok</span>
|
|
tx<span class="token operator">.</span><span class="token function">Commit<span class="token punctuation">(</span></span><span class="token operator">)</span>
|
|
</code></pre>
|
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<h3 id="a-specific-example">A Specific Example</h3>
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|
<pre><code class="lang-go"><span class="token keyword">func</span> <span class="token function">CreateAnimals<span class="token punctuation">(</span></span>db <span class="token operator">*</span>gorm<span class="token operator">.</span>DB<span class="token operator">)</span> err <span class="token operator">{</span>
|
|
tx <span class="token operator">:=</span> db<span class="token operator">.</span><span class="token function">Begin<span class="token punctuation">(</span></span><span class="token operator">)</span>
|
|
<span class="token comment" spellcheck="true">// Note the use of tx as the database handle once you are within a transaction</span>
|
|
|
|
<span class="token keyword">if</span> err <span class="token operator">:=</span> tx<span class="token operator">.</span><span class="token function">Create<span class="token punctuation">(</span></span><span class="token operator">&</span>Animal<span class="token operator">{</span>Name<span class="token operator">:</span> <span class="token string">"Giraffe"</span><span class="token operator">}</span><span class="token operator">)</span><span class="token operator">.</span>Error<span class="token operator">;</span> err <span class="token operator">!=</span> <span class="token boolean">nil</span> <span class="token operator">{</span>
|
|
tx<span class="token operator">.</span><span class="token function">Rollback<span class="token punctuation">(</span></span><span class="token operator">)</span>
|
|
<span class="token keyword">return</span> err
|
|
<span class="token operator">}</span>
|
|
|
|
<span class="token keyword">if</span> err <span class="token operator">:=</span> tx<span class="token operator">.</span><span class="token function">Create<span class="token punctuation">(</span></span><span class="token operator">&</span>Animal<span class="token operator">{</span>Name<span class="token operator">:</span> <span class="token string">"Lion"</span><span class="token operator">}</span><span class="token operator">)</span><span class="token operator">.</span>Error<span class="token operator">;</span> err <span class="token operator">!=</span> <span class="token boolean">nil</span> <span class="token operator">{</span>
|
|
tx<span class="token operator">.</span><span class="token function">Rollback<span class="token punctuation">(</span></span><span class="token operator">)</span>
|
|
<span class="token keyword">return</span> err
|
|
<span class="token operator">}</span>
|
|
|
|
tx<span class="token operator">.</span><span class="token function">Commit<span class="token punctuation">(</span></span><span class="token operator">)</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">nil</span>
|
|
<span class="token operator">}</span>
|
|
</code></pre>
|
|
<h2 id="raw-sql">Raw SQL</h2>
|
|
<pre><code class="lang-go">db<span class="token operator">.</span><span class="token function">Exec<span class="token punctuation">(</span></span><span class="token string">"DROP TABLE users;"</span><span class="token operator">)</span>
|
|
db<span class="token operator">.</span><span class="token function">Exec<span class="token punctuation">(</span></span><span class="token string">"UPDATE orders SET shipped_at=? WHERE id IN (?)"</span><span class="token operator">,</span> time<span class="token operator">.</span>Now<span class="token operator">,</span> <span class="token operator">[</span><span class="token operator">]</span><span class="token builtin">int64</span><span class="token operator">{</span><span class="token number">11</span><span class="token operator">,</span><span class="token number">22</span><span class="token operator">,</span><span class="token number">33</span><span class="token operator">}</span><span class="token operator">)</span>
|
|
</code></pre>
|
|
<h2 id="row--rows">Row & Rows</h2>
|
|
<p>It is even possible to get query result as <code>*sql.Row</code> or <code>*sql.Rows</code></p>
|
|
<pre><code class="lang-go">row <span class="token operator">:=</span> db<span class="token operator">.</span><span class="token function">Table<span class="token punctuation">(</span></span><span class="token string">"users"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Where<span class="token punctuation">(</span></span><span class="token string">"name = ?"</span><span class="token operator">,</span> <span class="token string">"jinzhu"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Select<span class="token punctuation">(</span></span><span class="token string">"name, age"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Row<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token comment" spellcheck="true">// (*sql.Row)</span>
|
|
row<span class="token operator">.</span><span class="token function">Scan<span class="token punctuation">(</span></span><span class="token operator">&</span>name<span class="token operator">,</span> <span class="token operator">&</span>age<span class="token operator">)</span>
|
|
|
|
rows<span class="token operator">,</span> err <span class="token operator">:=</span> db<span class="token operator">.</span><span class="token function">Model<span class="token punctuation">(</span></span><span class="token operator">&</span>User<span class="token operator">{</span><span class="token operator">}</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Where<span class="token punctuation">(</span></span><span class="token string">"name = ?"</span><span class="token operator">,</span> <span class="token string">"jinzhu"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Select<span class="token punctuation">(</span></span><span class="token string">"name, age, email"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Rows<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token comment" spellcheck="true">// (*sql.Rows, error)</span>
|
|
<span class="token keyword">defer</span> rows<span class="token operator">.</span><span class="token function">Close<span class="token punctuation">(</span></span><span class="token operator">)</span>
|
|
<span class="token keyword">for</span> rows<span class="token operator">.</span><span class="token function">Next<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token operator">{</span>
|
|
<span class="token operator">...</span>
|
|
rows<span class="token operator">.</span><span class="token function">Scan<span class="token punctuation">(</span></span><span class="token operator">&</span>name<span class="token operator">,</span> <span class="token operator">&</span>age<span class="token operator">,</span> <span class="token operator">&</span>email<span class="token operator">)</span>
|
|
<span class="token operator">...</span>
|
|
<span class="token operator">}</span>
|
|
|
|
<span class="token comment" spellcheck="true">// Raw SQL</span>
|
|
rows<span class="token operator">,</span> err <span class="token operator">:=</span> db<span class="token operator">.</span><span class="token function">Raw<span class="token punctuation">(</span></span><span class="token string">"select name, age, email from users where name = ?"</span><span class="token operator">,</span> <span class="token string">"jinzhu"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Rows<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token comment" spellcheck="true">// (*sql.Rows, error)</span>
|
|
<span class="token keyword">defer</span> rows<span class="token operator">.</span><span class="token function">Close<span class="token punctuation">(</span></span><span class="token operator">)</span>
|
|
<span class="token keyword">for</span> rows<span class="token operator">.</span><span class="token function">Next<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token operator">{</span>
|
|
<span class="token operator">...</span>
|
|
rows<span class="token operator">.</span><span class="token function">Scan<span class="token punctuation">(</span></span><span class="token operator">&</span>name<span class="token operator">,</span> <span class="token operator">&</span>age<span class="token operator">,</span> <span class="token operator">&</span>email<span class="token operator">)</span>
|
|
<span class="token operator">...</span>
|
|
<span class="token operator">}</span>
|
|
</code></pre>
|
|
<h3 id="scan-rows">Scan Rows</h3>
|
|
<pre><code class="lang-go">rows<span class="token operator">,</span> err <span class="token operator">:=</span> db<span class="token operator">.</span><span class="token function">Model<span class="token punctuation">(</span></span><span class="token operator">&</span>User<span class="token operator">{</span><span class="token operator">}</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Where<span class="token punctuation">(</span></span><span class="token string">"name = ?"</span><span class="token operator">,</span> <span class="token string">"jinzhu"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Select<span class="token punctuation">(</span></span><span class="token string">"name, age, email"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Rows<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token comment" spellcheck="true">// (*sql.Rows, error)</span>
|
|
<span class="token keyword">defer</span> rows<span class="token operator">.</span><span class="token function">Close<span class="token punctuation">(</span></span><span class="token operator">)</span>
|
|
|
|
<span class="token keyword">for</span> rows<span class="token operator">.</span><span class="token function">Next<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token operator">{</span>
|
|
<span class="token keyword">var</span> user User
|
|
db<span class="token operator">.</span><span class="token function">ScanRows<span class="token punctuation">(</span></span>rows<span class="token operator">,</span> <span class="token operator">&</span>user<span class="token operator">)</span>
|
|
<span class="token comment" spellcheck="true">// do something</span>
|
|
<span class="token operator">}</span>
|
|
</code></pre>
|
|
<h2 id="composite-primary-key">Composite Primary Key</h2>
|
|
<pre><code class="lang-go"><span class="token keyword">type</span> Product <span class="token keyword">struct</span> <span class="token operator">{</span>
|
|
ID <span class="token builtin">string</span> <span class="token string">`gorm:"primary_key"`</span>
|
|
LanguageCode <span class="token builtin">string</span> <span class="token string">`gorm:"primary_key"`</span>
|
|
<span class="token operator">}</span>
|
|
</code></pre>
|
|
<h2 id="logger">Logger</h2>
|
|
<p>Gorm has built-in logger support</p>
|
|
<pre><code class="lang-go"><span class="token comment" spellcheck="true">// Enable Logger</span>
|
|
db<span class="token operator">.</span><span class="token function">LogMode<span class="token punctuation">(</span></span><span class="token boolean">true</span><span class="token operator">)</span>
|
|
|
|
<span class="token comment" spellcheck="true">// Diable Logger</span>
|
|
db<span class="token operator">.</span><span class="token function">LogMode<span class="token punctuation">(</span></span><span class="token boolean">false</span><span class="token operator">)</span>
|
|
|
|
<span class="token comment" spellcheck="true">// Debug a single operation</span>
|
|
db<span class="token operator">.</span><span class="token function">Debug<span class="token punctuation">(</span></span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Where<span class="token punctuation">(</span></span><span class="token string">"name = ?"</span><span class="token operator">,</span> <span class="token string">"jinzhu"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">First<span class="token punctuation">(</span></span><span class="token operator">&</span>User<span class="token operator">{</span><span class="token operator">}</span><span class="token operator">)</span>
|
|
</code></pre>
|
|
<p><img src="https:/raw.github.com/jinzhu/gorm/master/doc/logger.png" alt="logger"></p>
|
|
<h3 id="customize-logger">Customize Logger</h3>
|
|
<pre><code class="lang-go"><span class="token comment" spellcheck="true">// Refer gorm's default logger for how to: https://github.com/jinzhu/gorm/blob/master/logger.go#files</span>
|
|
db<span class="token operator">.</span><span class="token function">SetLogger<span class="token punctuation">(</span></span>gorm<span class="token operator">.</span>Logger<span class="token operator">{</span>revel<span class="token operator">.</span>TRACE<span class="token operator">}</span><span class="token operator">)</span>
|
|
db<span class="token operator">.</span><span class="token function">SetLogger<span class="token punctuation">(</span></span>log<span class="token operator">.</span><span class="token function">New<span class="token punctuation">(</span></span>os<span class="token operator">.</span>Stdout<span class="token operator">,</span> <span class="token string">"\r\n"</span><span class="token operator">,</span> <span class="token number">0</span><span class="token operator">)</span><span class="token operator">)</span>
|
|
</code></pre>
|
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