Table test has created_at column, type=timestamp, length=3

use Illuminate\Support\Facades\DB;

DB::table('test')->insert(
    ['created_at' => now()->format("Y-m-d H:i:s.u")]
);

usleep(500000); // sleep 0.5s

DB::table('test')->insert(
    ['created_at' => now()->format("Y-m-d H:i:s.u")]
);