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			780 lines
		
	
	
		
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<!DOCTYPE HTML>
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        <title>Database · GORM Guide</title>
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    data-level="1"
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    data-chapter-title="Database"
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    data-filepath="database.md"
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    data-revision="Fri Feb 26 2016 21:50:14 GMT+0800 (CST)"
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                <a href="./">
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                    Getting Started with GORM
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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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                <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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                <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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                        <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 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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        <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 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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            </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 " 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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                        <b>6.</b>
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                    Development
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                </a>
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                        <b>6.1.</b>
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                    Write Plugins
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                </a>
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                        <div class="page-inner">
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                            <section class="normal markdown-section">
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                            <h1 id="database">Database</h1>
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<!-- toc -->
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<ul>
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<li><a href="#connecting-to-a-database">Connecting to a database</a><ul>
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<li><a href="#mysql">MySQL</a></li>
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<li><a href="#postgresql">PostgreSQL</a></li>
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<li><a href="#sqlite3">Sqlite3</a></li>
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<li><a href="#write-dialect-for-unsupported-databases">Write Dialect for unsupported databases</a></li>
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</ul>
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</li>
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<li><a href="#generic-database-object-sqldb">Generic database object *sql.DB</a></li>
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<li><a href="#migration">Migration</a><ul>
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<li><a href="#auto-migration">Auto Migration</a></li>
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<li><a href="#has-table">Has Table</a></li>
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<li><a href="#create-table">Create Table</a></li>
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<li><a href="#drop-table">Drop table</a></li>
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<li><a href="#modifycolumn">ModifyColumn</a></li>
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<li><a href="#dropcolumn">DropColumn</a></li>
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<li><a href="#add-foreign-key">Add Foreign Key</a></li>
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<li><a href="#indexes">Indexes</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="connecting-to-a-database">Connecting to a database</h2>
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<h4 id="mysql">MySQL</h4>
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<p><strong>NOTE</strong> don't forgot params <code>parseTime</code> to handle data type <code>time.Time</code>, <a href="https://github.com/go-sql-driver/mysql#parameters" target="_blank">more support parameters</a></p>
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<pre><code class="lang-go"><span class="token keyword">import</span> <span class="token operator">(</span>
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    <span class="token string">"github.com/jinzhu/gorm"</span>
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    <span class="token boolean">_</span> <span class="token string">"github.com/go-sql-driver/mysql"</span>
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<span class="token operator">)</span>
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<span class="token keyword">func</span> <span class="token function">main<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token operator">{</span>
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  db<span class="token operator">,</span> err <span class="token operator">:=</span> gorm<span class="token operator">.</span><span class="token function">Open<span class="token punctuation">(</span></span><span class="token string">"mysql"</span><span class="token operator">,</span> <span class="token string">"user:password@/dbname?charset=utf8&parseTime=True&loc=Local"</span><span class="token operator">)</span>
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<span class="token operator">}</span>
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</code></pre>
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<h4 id="postgresql">PostgreSQL</h4>
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<pre><code class="lang-go"><span class="token keyword">import</span> <span class="token operator">(</span>
 | 
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    <span class="token string">"github.com/jinzhu/gorm"</span>
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    <span class="token boolean">_</span> <span class="token string">"github.com/lib/pq"</span>
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<span class="token operator">)</span>
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<span class="token keyword">func</span> <span class="token function">main<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token operator">{</span>
 | 
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  db<span class="token operator">,</span> err <span class="token operator">:=</span> gorm<span class="token operator">.</span><span class="token function">Open<span class="token punctuation">(</span></span><span class="token string">"postgres"</span><span class="token operator">,</span> <span class="token string">"user=gorm dbname=gorm sslmode=disable"</span><span class="token operator">)</span>
 | 
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<span class="token operator">}</span>
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</code></pre>
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<h4 id="sqlite3">Sqlite3</h4>
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<pre><code class="lang-go"><span class="token keyword">import</span> <span class="token operator">(</span>
 | 
						|
    <span class="token string">"github.com/jinzhu/gorm"</span>
 | 
						|
    <span class="token boolean">_</span> <span class="token string">"github.com/mattn/go-sqlite3"</span>
 | 
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<span class="token operator">)</span>
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<span class="token keyword">func</span> <span class="token function">main<span class="token punctuation">(</span></span><span class="token operator">)</span> <span class="token operator">{</span>
 | 
						|
  db<span class="token operator">,</span> err <span class="token operator">:=</span> gorm<span class="token operator">.</span><span class="token function">Open<span class="token punctuation">(</span></span><span class="token string">"sqlite3"</span><span class="token operator">,</span> <span class="token string">"/tmp/gorm.db"</span><span class="token operator">)</span>
 | 
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<span class="token operator">}</span>
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</code></pre>
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<h4 id="write-dialect-for-unsupported-databases">Write Dialect for unsupported databases</h4>
 | 
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<p>GORM officially support above databases, for unsupported databaes, you could write a dialect for that.</p>
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<p>Refer: <a href="https://github.com/jinzhu/gorm/blob/master/dialect.go" target="_blank">https://github.com/jinzhu/gorm/blob/master/dialect.go</a></p>
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<h2 id="generic-database-object-sqldb">Generic database object *sql.DB</h2>
 | 
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<p><a href="http://golang.org/pkg/database/sql/#DB" target="_blank">*sql.DB</a></p>
 | 
						|
<pre><code class="lang-go"><span class="token comment" spellcheck="true">// Get generic database object *sql.DB to use its functions</span>
 | 
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db<span class="token operator">.</span><span class="token function">DB<span class="token punctuation">(</span></span><span class="token operator">)</span>
 | 
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<span class="token comment" spellcheck="true">// Connection Pool</span>
 | 
						|
db<span class="token operator">.</span><span class="token function">DB<span class="token punctuation">(</span></span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">SetMaxIdleConns<span class="token punctuation">(</span></span><span class="token number">10</span><span class="token operator">)</span>
 | 
						|
db<span class="token operator">.</span><span class="token function">DB<span class="token punctuation">(</span></span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">SetMaxOpenConns<span class="token punctuation">(</span></span><span class="token number">100</span><span class="token operator">)</span>
 | 
						|
 | 
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  <span class="token comment" spellcheck="true">// Ping</span>
 | 
						|
db<span class="token operator">.</span><span class="token function">DB<span class="token punctuation">(</span></span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">Ping<span class="token punctuation">(</span></span><span class="token operator">)</span>
 | 
						|
</code></pre>
 | 
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<h2 id="migration">Migration</h2>
 | 
						|
<!-- toc -->
 | 
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<h3 id="auto-migration">Auto Migration</h3>
 | 
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<p>Automatically migrate your schema, to keep your schema update to date</p>
 | 
						|
<p><strong>WARNING</strong> AutoMigrate will ONLY create tables, columns and indexes if doesn't exist,
 | 
						|
WON'T change existing column's type or delete unused columns to protect your data</p>
 | 
						|
<pre><code class="lang-go">db<span class="token operator">.</span><span class="token function">AutoMigrate<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>
 | 
						|
 | 
						|
db<span class="token operator">.</span><span class="token function">AutoMigrate<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>Product<span class="token operator">{</span><span class="token operator">}</span><span class="token operator">,</span> <span class="token operator">&</span>Order<span class="token operator">{</span><span class="token operator">}</span><span class="token operator">)</span>
 | 
						|
 | 
						|
<span class="token comment" spellcheck="true">// Add table suffix when create tables</span>
 | 
						|
db<span class="token operator">.</span><span class="token function">Set<span class="token punctuation">(</span></span><span class="token string">"gorm:table_options"</span><span class="token operator">,</span> <span class="token string">"ENGINE=InnoDB"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">AutoMigrate<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>
 | 
						|
<h3 id="has-table">Has Table</h3>
 | 
						|
<pre><code class="lang-go"><span class="token comment" spellcheck="true">// Check if model `User`'s table has been created or not</span>
 | 
						|
db<span class="token operator">.</span><span class="token function">HasTable<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 comment" spellcheck="true">// Check table `users` exists or not</span>
 | 
						|
db<span class="token operator">.</span><span class="token function">HasTable<span class="token punctuation">(</span></span><span class="token string">"users"</span><span class="token operator">)</span>
 | 
						|
</code></pre>
 | 
						|
<h3 id="create-table">Create Table</h3>
 | 
						|
<pre><code class="lang-go">db<span class="token operator">.</span><span class="token function">CreateTable<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>
 | 
						|
 | 
						|
db<span class="token operator">.</span><span class="token function">Set<span class="token punctuation">(</span></span><span class="token string">"gorm:table_options"</span><span class="token operator">,</span> <span class="token string">"ENGINE=InnoDB"</span><span class="token operator">)</span><span class="token operator">.</span><span class="token function">CreateTable<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 comment" spellcheck="true">// will append "ENGINE=InnoDB" to the SQL statement when creating table `users`</span>
 | 
						|
</code></pre>
 | 
						|
<h3 id="drop-table">Drop table</h3>
 | 
						|
<pre><code class="lang-go">db<span class="token operator">.</span><span class="token function">DropTable<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>
 | 
						|
<h3 id="modifycolumn">ModifyColumn</h3>
 | 
						|
<p>Change column's type</p>
 | 
						|
<pre><code class="lang-go"><span class="token comment" spellcheck="true">// change column description's data type to `text` for model `User`'s table</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">ModifyColumn<span class="token punctuation">(</span></span><span class="token string">"description"</span><span class="token operator">,</span> <span class="token string">"text"</span><span class="token operator">)</span>
 | 
						|
</code></pre>
 | 
						|
<h3 id="dropcolumn">DropColumn</h3>
 | 
						|
<pre><code class="lang-go">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">DropColumn<span class="token punctuation">(</span></span><span class="token string">"description"</span><span class="token operator">)</span>
 | 
						|
</code></pre>
 | 
						|
<h3 id="add-foreign-key">Add Foreign Key</h3>
 | 
						|
<pre><code class="lang-go"><span class="token comment" spellcheck="true">// Add foreign key</span>
 | 
						|
<span class="token comment" spellcheck="true">// 1st param : foreignkey field</span>
 | 
						|
<span class="token comment" spellcheck="true">// 2nd param : destination table(id)</span>
 | 
						|
<span class="token comment" spellcheck="true">// 3rd param : ONDELETE</span>
 | 
						|
<span class="token comment" spellcheck="true">// 4th param : ONUPDATE</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">AddForeignKey<span class="token punctuation">(</span></span><span class="token string">"city_id"</span><span class="token operator">,</span> <span class="token string">"cities(id)"</span><span class="token operator">,</span> <span class="token string">"RESTRICT"</span><span class="token operator">,</span> <span class="token string">"RESTRICT"</span><span class="token operator">)</span>
 | 
						|
</code></pre>
 | 
						|
<h3 id="indexes">Indexes</h3>
 | 
						|
<pre><code class="lang-go"><span class="token comment" spellcheck="true">// Add index</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">AddIndex<span class="token punctuation">(</span></span><span class="token string">"idx_user_name"</span><span class="token operator">,</span> <span class="token string">"name"</span><span class="token operator">)</span>
 | 
						|
 | 
						|
<span class="token comment" spellcheck="true">// Multiple column index</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">AddIndex<span class="token punctuation">(</span></span><span class="token string">"idx_user_name_age"</span><span class="token operator">,</span> <span class="token string">"name"</span><span class="token operator">,</span> <span class="token string">"age"</span><span class="token operator">)</span>
 | 
						|
 | 
						|
<span class="token comment" spellcheck="true">// Add unique index</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">AddUniqueIndex<span class="token punctuation">(</span></span><span class="token string">"idx_user_name"</span><span class="token operator">,</span> <span class="token string">"name"</span><span class="token operator">)</span>
 | 
						|
 | 
						|
<span class="token comment" spellcheck="true">// Multiple column unique index</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">AddUniqueIndex<span class="token punctuation">(</span></span><span class="token string">"idx_user_name_age"</span><span class="token operator">,</span> <span class="token string">"name"</span><span class="token operator">,</span> <span class="token string">"age"</span><span class="token operator">)</span>
 | 
						|
 | 
						|
<span class="token comment" spellcheck="true">// Remove index</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">RemoveIndex<span class="token punctuation">(</span></span><span class="token string">"idx_user_name"</span><span class="token operator">)</span>
 | 
						|
</code></pre>
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                            </section>
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