Database: Getting Started

Introduction

Laravel makes interacting with databases extremely simple across a variety of database backends using either raw SQL, the fluent query builder, and the Eloquent ORM. Currently, Laravel supports four databases:

• MySQL
• PostgreSQL
• SQLite
• SQL Server

Configuration

The database configuration for your application is located at config/database.php. In this file you may define all of your database connections, as well as specify which connection should be used by default. Examples for most of the supported database systems are provided in this file.

By default, Laravel's sample environment configuration is ready to use with Laravel Homestead, which is a convenient virtual machine for doing Laravel development on your local machine. Of course, you are free to modify this configuration as needed for your local database.

SQLite Configuration

After creating a new SQLite database using a command such as touch database/database.sqlite, you can easily configure your environment variables to point to this newly created database by using the database's absolute path:

DB_CONNECTION=sqlite
DB_DATABASE=/absolute/path/to/database.sqlite

Read & Write Connections

Sometimes you may wish to use one database connection for SELECT statements, and another for INSERT, UPDATE, and DELETE statements. Laravel makes this a breeze, and the proper connections will always be used whether you are using raw queries, the query builder, or the Eloquent ORM.

To see how read / write connections should be configured, let's look at this example:

'mysql' => [
    'read' => [
        'host' => ['192.168.1.1'],
    ],
    'write' => [
        'host' => ['196.168.1.2'],
    ],
    'sticky'    => true,
    'driver'    => 'mysql',
    'database'  => 'database',
    'username'  => 'root',
    'password'  => '',
    'charset'   => 'utf8mb4',
    'collation' => 'utf8mb4_unicode_ci',
    'prefix'    => '',
],

Note that three keys have been added to the configuration array: read, write and sticky. The read and write keys have array values containing a single key: host. The rest of the database options for the read and write connections will be merged from the main mysql array.

You only need to place items in the read and write arrays if you wish to override the values from the main array. So, in this case, 192.168.1.1 will be used as the host for the "read" connection, while 192.168.1.2 will be used for the "write" connection. The database credentials, prefix, character set, and all other options in the main mysql array will be shared across both connections.

The sticky Option

The sticky option is an optional value that can be used to allow the immediate reading of records that have been written to the database during the current request cycle. If the sticky option is enabled and a "write" operation has been performed against the database during the current request cycle, any further "read" operations will use the "write" connection. This ensures that any data written during the request cycle can be immediately read back from the database during that same request. It is up to you to decide if this is the desired behavior for your application.

Using Multiple Database Connections

When using multiple connections, you may access each connection via the connection method on the DB facade. The name passed to the connection method should correspond to one of the connections listed in your config/database.php configuration file:

$users = DB::connection('foo')->select(...);

You may also access the raw, underlying PDO instance using the getPdo method on a connection instance:

$pdo = DB::connection()->getPdo();

Running Raw SQL Queries

Once you have configured your database connection, you may run queries using the DB facade. The DB facade provides methods for each type of query: select, update, insert, delete, and statement.

Running A Select Query

To run a basic query, you may use the select method on the DB facade:

<?php

namespace App\Http\Controllers;

use Illuminate\Support\Facades\DB;
use App\Http\Controllers\Controller;

class UserController extends Controller
{
    /**
     * Show a list of all of the application's users.
     *
     * @return Response
     */
    public function index()
    {
        $users = DB::select('select * from users where active = ?', [1]);

        return view('user.index', ['users' => $users]);
    }
}

The first argument passed to the select method is the raw SQL query, while the second argument is any parameter bindings that need to be bound to the query. Typically, these are the values of the where clause constraints. Parameter binding provides protection against SQL injection.

The select method will always return an array of results. Each result within the array will be a PHP stdClass object, allowing you to access the values of the results:

foreach ($users as $user) {
    echo $user->name;
}

Using Named Bindings

Instead of using ? to represent your parameter bindings, you may execute a query using named bindings:

$results = DB::select('select * from users where id = :id', ['id' => 1]);

Running An Insert Statement

To execute an insert statement, you may use the insert method on the DB facade. Like select, this method takes the raw SQL query as its first argument and bindings as its second argument:

DB::insert('insert into users (id, name) values (?, ?)', [1, 'Dayle']);

Running An Update Statement

The update method should be used to update existing records in the database. The number of rows affected by the statement will be returned:

$affected = DB::update('update users set votes = 100 where name = ?', ['John']);

Running A Delete Statement

The delete method should be used to delete records from the database. Like update, the number of rows affected will be returned:

$deleted = DB::delete('delete from users');

Running A General Statement

Some database statements do not return any value. For these types of operations, you may use the statement method on the DB facade:

DB::statement('drop table users');

Listening For Query Events

If you would like to receive each SQL query executed by your application, you may use the listen method. This method is useful for logging queries or debugging. You may register your query listener in a service provider:

<?php

namespace App\Providers;

use Illuminate\Support\Facades\DB;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        DB::listen(function ($query) {
            // $query->sql
            // $query->bindings
            // $query->time
        });
    }

    /**
     * Register the service provider.
     *
     * @return void
     */
    public function register()
    {
        //
    }
}

Database Transactions

You may use the transaction method on the DB facade to run a set of operations within a database transaction. If an exception is thrown within the transaction Closure, the transaction will automatically be rolled back. If the Closure executes successfully, the transaction will automatically be committed. You don't need to worry about manually rolling back or committing while using the transaction method:

DB::transaction(function () {
    DB::table('users')->update(['votes' => 1]);

    DB::table('posts')->delete();
});

Handling Deadlocks

The transaction method accepts an optional second argument which defines the number of times a transaction should be reattempted when a deadlock occurs. Once these attempts have been exhausted, an exception will be thrown:

DB::transaction(function () {
    DB::table('users')->update(['votes' => 1]);

    DB::table('posts')->delete();
}, 5);

Manually Using Transactions

If you would like to begin a transaction manually and have complete control over rollbacks and commits, you may use the beginTransaction method on the DB facade:

DB::beginTransaction();

You can rollback the transaction via the rollBack method:

DB::rollBack();

Lastly, you can commit a transaction via the commit method:

DB::commit();

提示

The DB facade's transaction methods control the transactions for both the query builder and Eloquent ORM.