how to migrate new column without empty the table in laravel

1Use below command to modify the existing table
2
3php artisan make:migration add_shipped_via_and_terms_colums_to_purchase_orders_table --table=purchase_orders
4use --create for creating the new table and --table for modifying the existing table.
5
6Now a new migration file will be created. Inside the up() function in this file add these line
7
8Schema::table('purchase_orders', function(Blueprint $table){
9    $table->string('shipped_via');
10    $table->string('terms');
11});
12And then run php artisan migrate

1php artisan make:migration add_shipped_via_and_terms_colums_to_purchase_orders_table --table=purchase_orders