Với Laravel Migration, Làm cách nào để thay đổi kiểu dữ liệu của một cột và cập nhật dữ liệu hiện có của nó để phù hợp với kiểu dữ liệu mới mà không cần sử dụng các truy vấn SQL thô?

Đây là cách tôi thực hiện việc này:

Phương thức up ():

...
use App\User;

/**
 * Run the migrations.
 *
 * @return void
 */
public function up()
{
    // do the following steps in order:
    // 1- add a new column with the desired data type to the table
    // 2- fill the new column with the appropriate data
    // 3- delete the old column
    // 4- rename the new column to match name of the deleted column

    Schema::table('users', function(Blueprint $table)
    {
        // 1- add a new column with the desired data type to the table
        // note that after() method is used to order the column and works only with MySQL
        $table->boolean('is_suspended_new')->default(0)->after('is_suspended');
    });

    // 2- fill the new column with the appropriate data 
    // note that you may need to use data in the old column as a guide (like in this example)
    $users = User::all();
    if ($users) {
        foreach ($users as $user) {
            $u = User::find($user->id);

            if ($u->is_suspended === 'yes') {
                $u->is_suspended_new = 1;
            } elseif ($u->is_suspended === 'no') {
                $u->is_suspended_new = 0;
            }

            $u->save();
        }
    }

    Schema::table('users', function(Blueprint $table)
    {
        // 3- delete the old column
        $table->dropColumn('is_suspended');
    });

    Schema::table('users', function(Blueprint $table)
    {
        // 4- rename the new column to match name of the deleted column
        $table->renameColumn('is_suspended_new', 'is_suspended');
    });
}

Phương thức down ():

/**
 * Reverse the migrations.
 *
 * @return void
 */
public function down()
{
    // IMPORTANT NOTE:
    // because renaming (enum) column types is not supported in laravel 4.2 (as mentioned here https://laravel.com/docs/4.2/schema#renaming-columns)
    // so we will make some changes in the order of the steps as follows:
    // 
    // do the following steps in order:
    // 1- rename the exiting column
    // 2- add a new column with the desired data type and give it a name matches name of the existing column before renaming
    // 3- fill the new column with the appropriate data
    // 4- delete the old column

    Schema::table('users', function(Blueprint $table)
    {
        // 1- rename the existing column
        $table->renameColumn('is_suspended', 'is_suspended_old');
    });

    Schema::table('users', function(Blueprint $table)
    {
        // 2- add a new column with the desired data type to the table
        // and give it a name matches name of the existing column before renaming
        // note that after() method is used to order the column and works only with MySQL
        $table->enum('is_suspended', ['yes', 'no'])->default('no')->after('is_suspended_old');
    });

    // 3- fill the new column with the approprite data 
    // note that you may need to use data in the old column as a guide (like in this example)
    $users = User::all();
    if ($users) {
        foreach ($users as $user) {
            $u = User::find($user->id);

            if ($u->is_suspended_old == 1) {
                $u->is_suspended = 'yes';
            } elseif ($u->is_suspended_old == 0) {
                $u->is_suspended = 'no';
            }

            $u->save();
        }
    }

    Schema::table('users', function(Blueprint $table)
    {
        // 4- delete the old column
        $table->dropColumn('is_suspended_old');
    });
}