Laravel禁止对Alias自动加表前缀

前言

使用DB::table('menu as m')->get()生成的SQL语句是select * from menu as prefix_m，可见Laravel自动给alias加了表前缀，可以通过预先注册Grammar实现的方式修改。

• 缺点：不同数据库引擎需要分别编写不同的实现
• 优点：简单可靠方便

使用后，SQL语句变成了select * from menu as m

适用版本：Laravel5.x、Laravel7.x （6.x未测试）

代码

<?php
namespace App\Providers\patch;

use \Illuminate\Database\Query\Builder;

/**
 * Class MysqlGrammar
 * @author Student414
 * @date 2020-5-21
 */
class MysqlGrammar extends \Illuminate\Database\Query\Grammars\MySqlGrammar
{

    /**
     * Wrap a table in keyword identifiers.
     *
     * @param  \Illuminate\Database\Query\Expression|string  $table
     * @return string
     */
    public function wrapTable($table)
    {
        if (!$this->isExpression($table)) {
            return $this->wrap($this->tablePrefix . $table, false); // hack
        }

        return $this->getValue($table);
    }

    /**
     * Wrap the given value segments.
     *
     * @param  array  $segments
     * @return string
     */
    protected function wrapSegments($segments)
    {
        return collect($segments)->map(function ($segment, $key) use ($segments) {
            return $key == 0 && count($segments) > 1
            ? $this->wrap($segment) // hack
            : $this->wrapValue($segment);
        })->implode('.');
    }
}

<?php
namespace App\Providers\patch;

/**
 * Class MysqlConnection
 */
class MysqlConnection extends \Illuminate\Database\Connection
{
    /**
     * @return MysqlGrammar
     */
    protected function getDefaultQueryGrammar()
    {
        return $this->withTablePrefix(new MysqlGrammar()); // here comes our custom Grammar object
    }
}

<?php

namespace App\Providers;

use App\Providers\patch\MysqlConnection;
use Illuminate\Database\Connection;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        Connection::resolverFor('mysql', function ($connection, $database, $prefix, $config) {
            return new MysqlConnection($connection, $database, $prefix, $config);
        });

        // 也可以使用这个替换Grammar实现
        // $this->app->get('db.connection')->setQueryGrammar(new MysqlGrammar());
    }
}

参考资料

https://medium.com/@daniilromazanov/how-to-extend-query-grammar-in-laravel-fb3d2d6de6d4

PS：还可以通过反射实现，动态替换Grammar实现，但是优缺点和此方案相同，不建议使用。