[SloProKiller]

If I understand correctly, you want to make players only able to join a deathmatch once someone is in it. If so, here is the code.

pawn Код:

CMD:dm(playerid, params[])
{
    new pcount;
    for(new i = 0; i < MAX_PLAYERS; i++)
    {
        if(IsPlayerConnected(i)) pcount ++;
    }
    if(!pcount) return SendClientMessage(playerid, 0xFFFFFFFF, "Not enough players to join");
    else
    {
        //your join deathmatch code here
    }
    return 1;
}

Remember to add pcount --; once players leave the deathmatch.