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Getting Started with GORM
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<b>1.</b>
Database
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<li class="chapter " data-level="1.1" data-path="database.html">
<a href="database.html#connecting-to-a-database">
<b>1.1.</b>
Database Connection
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<a href="database.html#migration">
<b>1.2.</b>
Migration
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<b>2.</b>
Models
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<b>2.1.</b>
Model Definition
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<b>2.2.</b>
Conventions &amp; Overriding
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<b>2.3.</b>
Associations
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<b>2.3.1.</b>
Belongs To
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<b>2.3.2.</b>
Has One
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<b>2.3.3.</b>
Has Many
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<a href="associations.html#many-to-many">
<b>2.3.4.</b>
Many To Many
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<b>2.3.5.</b>
Polymorphism
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<b>2.3.6.</b>
Association Mode
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<b>3.</b>
CRUD: Reading and Writing Data
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<a href="curd.html#create">
<b>3.1.</b>
Create
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<b>3.2.</b>
Query
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<b>3.3.</b>
Preloading (Eager Loading)
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<b>3.4.</b>
Update
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<b>3.5.</b>
Delete / Soft Delete
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<b>4.</b>
Callbacks
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<b>5.</b>
Advanced Usage
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<b>5.1.</b>
Error Handling
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<b>5.2.</b>
Transactions
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<a href="advanced.html#sql-builder">
<b>5.3.</b>
Raw SQL &amp; SQL Builder
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<a href="advanced.html#generic-database-interface-sqldb">
<b>5.4.</b>
Generic database interface sql.DB
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<a href="advanced.html#compose-primary-key">
<b>5.5.</b>
Composite Primary Key
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<b>5.6.</b>
Overriding Logger
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<b>6.</b>
Development
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<b>6.1.</b>
Architecture
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<b>6.2.</b>
Write Plugins
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<b>7.</b>
Change Log
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<h1 id="database">Database</h1>
<!-- toc -->
<ul>
<li><a href="#connecting-to-a-database">Connecting to a database</a><ul>
<li><a href="#mysql">MySQL</a></li>
<li><a href="#postgresql">PostgreSQL</a></li>
<li><a href="#sqlite3">Sqlite3</a></li>
<li><a href="#write-dialect-for-unsupported-databases">Write Dialect for unsupported databases</a></li>
</ul>
</li>
<li><a href="#migration">Migration</a><ul>
<li><a href="#auto-migration">Auto Migration</a></li>
<li><a href="#has-table">Has Table</a></li>
<li><a href="#create-table">Create Table</a></li>
<li><a href="#drop-table">Drop table</a></li>
<li><a href="#modifycolumn">ModifyColumn</a></li>
<li><a href="#dropcolumn">DropColumn</a></li>
<li><a href="#add-foreign-key">Add Foreign Key</a></li>
<li><a href="#indexes">Indexes</a></li>
</ul>
</li>
</ul>
<!-- toc stop -->
<h2 id="connecting-to-a-database">Connecting to a database</h2>
<p>In order to connect to a database, you need to import the database&apos;s driver first. For example:</p>
<pre><code class="lang-go"><span class="hljs-keyword">import</span> _ <span class="hljs-string">&quot;github.com/go-sql-driver/mysql&quot;</span>
</code></pre>
<p>GORM has wrapped some drivers, for easier to remember the import path, so you could import the mysql driver with</p>
<pre><code class="lang-go"><span class="hljs-keyword">import</span> _ <span class="hljs-string">&quot;github.com/jinzhu/gorm/dialects/mysql&quot;</span>
<span class="hljs-comment">// import _ &quot;github.com/jinzhu/gorm/dialects/postgres&quot;</span>
<span class="hljs-comment">// import _ &quot;github.com/jinzhu/gorm/dialects/sqlite&quot;</span>
<span class="hljs-comment">// import _ &quot;github.com/jinzhu/gorm/dialects/mssql&quot;</span>
</code></pre>
<h4 id="mysql">MySQL</h4>
<p><strong>NOTE:</strong> In order to handle <code>time.Time</code>, you need to include <code>parseTime</code> as a parameter. (<a href="https://github.com/go-sql-driver/mysql#parameters" target="_blank">More supported parameters</a>)</p>
<pre><code class="lang-go"><span class="hljs-keyword">import</span> (
<span class="hljs-string">&quot;github.com/jinzhu/gorm&quot;</span>
_ <span class="hljs-string">&quot;github.com/jinzhu/gorm/dialects/mysql&quot;</span>
)
<span class="hljs-keyword">func</span> main() {
db, err := gorm.Open(<span class="hljs-string">&quot;mysql&quot;</span>, <span class="hljs-string">&quot;user:password@/dbname?charset=utf8&amp;parseTime=True&amp;loc=Local&quot;</span>)
}
</code></pre>
<h4 id="postgresql">PostgreSQL</h4>
<pre><code class="lang-go"><span class="hljs-keyword">import</span> (
<span class="hljs-string">&quot;github.com/jinzhu/gorm&quot;</span>
_ <span class="hljs-string">&quot;github.com/jinzhu/gorm/dialects/postgres&quot;</span>
)
<span class="hljs-keyword">func</span> main() {
db, err := gorm.Open(<span class="hljs-string">&quot;postgres&quot;</span>, <span class="hljs-string">&quot;host=myhost user=gorm dbname=gorm sslmode=disable password=mypassword&quot;</span>)
}
</code></pre>
<h4 id="sqlite3">Sqlite3</h4>
<pre><code class="lang-go"><span class="hljs-keyword">import</span> (
<span class="hljs-string">&quot;github.com/jinzhu/gorm&quot;</span>
_ <span class="hljs-string">&quot;github.com/jinzhu/gorm/dialects/sqlite&quot;</span>
)
<span class="hljs-keyword">func</span> main() {
db, err := gorm.Open(<span class="hljs-string">&quot;sqlite3&quot;</span>, <span class="hljs-string">&quot;/tmp/gorm.db&quot;</span>)
}
</code></pre>
<h4 id="write-dialect-for-unsupported-databases">Write Dialect for unsupported databases</h4>
<p>GORM officially supports the above databases, but you could write a dialect for unsupported databases.</p>
<p>To write your own dialect, refer to: <a href="https://github.com/jinzhu/gorm/blob/master/dialect.go" target="_blank">https://github.com/jinzhu/gorm/blob/master/dialect.go</a></p>
<h2 id="migration">Migration</h2>
<h3 id="auto-migration">Auto Migration</h3>
<p>Automatically migrate your schema, to keep your schema update to date.</p>
<p><strong>WARNING:</strong> AutoMigrate will <strong>ONLY</strong> create tables, missing columns and missing indexes, and <strong>WON&apos;T</strong> change existing column&apos;s type or delete unused columns to protect your data.</p>
<pre><code class="lang-go">db.AutoMigrate(&amp;User{})
db.AutoMigrate(&amp;User{}, &amp;Product{}, &amp;Order{})
<span class="hljs-comment">// Add table suffix when create tables</span>
db.Set(<span class="hljs-string">&quot;gorm:table_options&quot;</span>, <span class="hljs-string">&quot;ENGINE=InnoDB&quot;</span>).AutoMigrate(&amp;User{})
</code></pre>
<h3 id="has-table">Has Table</h3>
<pre><code class="lang-go"><span class="hljs-comment">// Check model `User`&apos;s table exists or not</span>
db.HasTable(&amp;User{})
<span class="hljs-comment">// Check table `users` exists or not</span>
db.HasTable(<span class="hljs-string">&quot;users&quot;</span>)
</code></pre>
<h3 id="create-table">Create Table</h3>
<pre><code class="lang-go"><span class="hljs-comment">// Create table for model `User`</span>
db.CreateTable(&amp;User{})
<span class="hljs-comment">// will append &quot;ENGINE=InnoDB&quot; to the SQL statement when creating table `users`</span>
db.Set(<span class="hljs-string">&quot;gorm:table_options&quot;</span>, <span class="hljs-string">&quot;ENGINE=InnoDB&quot;</span>).CreateTable(&amp;User{})
</code></pre>
<h3 id="drop-table">Drop table</h3>
<pre><code class="lang-go"><span class="hljs-comment">// Drop model `User`&apos;s table</span>
db.DropTable(&amp;User{})
<span class="hljs-comment">// Drop table `users</span>
db.DropTable(<span class="hljs-string">&quot;users&quot;</span>)
<span class="hljs-comment">// Drop model&apos;s `User`&apos;s table and table `products`</span>
db.DropTableIfExists(&amp;User{}, <span class="hljs-string">&quot;products&quot;</span>)
</code></pre>
<h3 id="modifycolumn">ModifyColumn</h3>
<p>Modify column&apos;s type to given value</p>
<pre><code class="lang-go"><span class="hljs-comment">// change column description&apos;s data type to `text` for model `User`</span>
db.Model(&amp;User{}).ModifyColumn(<span class="hljs-string">&quot;description&quot;</span>, <span class="hljs-string">&quot;text&quot;</span>)
</code></pre>
<h3 id="dropcolumn">DropColumn</h3>
<pre><code class="lang-go"><span class="hljs-comment">// Drop column description from model `User`</span>
db.Model(&amp;User{}).DropColumn(<span class="hljs-string">&quot;description&quot;</span>)
</code></pre>
<h3 id="add-foreign-key">Add Foreign Key</h3>
<pre><code class="lang-go"><span class="hljs-comment">// Add foreign key</span>
<span class="hljs-comment">// 1st param : foreignkey field</span>
<span class="hljs-comment">// 2nd param : destination table(id)</span>
<span class="hljs-comment">// 3rd param : ONDELETE</span>
<span class="hljs-comment">// 4th param : ONUPDATE</span>
db.Model(&amp;User{}).AddForeignKey(<span class="hljs-string">&quot;city_id&quot;</span>, <span class="hljs-string">&quot;cities(id)&quot;</span>, <span class="hljs-string">&quot;RESTRICT&quot;</span>, <span class="hljs-string">&quot;RESTRICT&quot;</span>)
</code></pre>
<h3 id="indexes">Indexes</h3>
<pre><code class="lang-go"><span class="hljs-comment">// Add index for columns `name` with given name `idx_user_name`</span>
db.Model(&amp;User{}).AddIndex(<span class="hljs-string">&quot;idx_user_name&quot;</span>, <span class="hljs-string">&quot;name&quot;</span>)
<span class="hljs-comment">// Add index for columns `name`, `age` with given name `idx_user_name_age`</span>
db.Model(&amp;User{}).AddIndex(<span class="hljs-string">&quot;idx_user_name_age&quot;</span>, <span class="hljs-string">&quot;name&quot;</span>, <span class="hljs-string">&quot;age&quot;</span>)
<span class="hljs-comment">// Add unique index</span>
db.Model(&amp;User{}).AddUniqueIndex(<span class="hljs-string">&quot;idx_user_name&quot;</span>, <span class="hljs-string">&quot;name&quot;</span>)
<span class="hljs-comment">// Add unique index for multiple columns</span>
db.Model(&amp;User{}).AddUniqueIndex(<span class="hljs-string">&quot;idx_user_name_age&quot;</span>, <span class="hljs-string">&quot;name&quot;</span>, <span class="hljs-string">&quot;age&quot;</span>)
<span class="hljs-comment">// Remove index</span>
db.Model(&amp;User{}).RemoveIndex(<span class="hljs-string">&quot;idx_user_name&quot;</span>)
</code></pre>
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