moderator-bot/handlers/groups/new_chat_member.py

from load import dp, types
from database import Member


@dp.message_handler(content_types=["new_chat_members"])
async def welcome_message(message: types.Message):
    user = Member.get_or_none(Member.user_id == message.from_user.id)

    if (user):
        await message.answer(f"Hi, {user.first_name} again")

    if not (user):
        Member.create(
            user_id=message.from_user.id,
            first_name=message.from_user.first_name,
            username=message.from_user.username,
        )

        await message.answer((
            f"Hi, **{user.first_name}**!\n"
            "Please, read [chat rules]({})"
            ).format("https://nometa.xyz"),
            parse_mode="Markdown"
        )

    await message.delete()