[Scenario]

I believe I do, actually...

OnGameModeInit - OnPlayerDisconnect

pawn Code:

public OnGameModeInit()
{
    mysql_init();
    mysql_connect(SQL_HOST, SQL_USER, SQL_PASS, SQL_DATA);
    
    AntiDeAMX();
    ShowNameTags(0);
    
    SetGameModeText(SVERSION);

    new sendcmd[50];
    format(sendcmd, sizeof(sendcmd), "hostname %s", ServerName);
    SendRconCommand(sendcmd);
    
    SetTimer("AAC", 21600000, true);
    
    LoadVehiclesFromDatabase();
    return 1;
}

public OnGameModeExit()
{
    for(new i = 0; i < MAX_PLAYERS; i++)
    {
        if(IsPlayerConnectedEx(i))
        {
            GetPlayerPos(i, PlayerStatistics[i][pPositionX], PlayerStatistics[i][pPositionY], PlayerStatistics[i][pPositionZ]);
            SavePlayerAccount(i);
        }
        else
        {
            return 1;
        }
    }
    mysql_close();
    return 1;
}

public OnPlayerConnect(playerid)
{
    format(string, sizeof(string), "%s has joined the server.", GetName(playerid));
    SendClientMessageToAll(COLOR_GREY, string);
    SetPlayerColor(playerid, PlayerColor);

    InitPlayerConnection(playerid);
    return 1;
}

public OnPlayerDisconnect(playerid, reason)
{
    format(string, sizeof(string), "%s has left the server.", GetName(playerid));
    SendClientMessageToAll(COLOR_GREY, string);

    SavePlayerAccount(playerid);
    return 1;
}

The rest...

pawn Code:

public OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])
{
    switch(dialogid)
    {
        case 1:
        {
            if(!response) // If the player hit "exit" we're going to kick them
            {
                SendClientMessage(playerid, COLOR_RED, "You selected exit, therefore you were kicked.");
                Kick(playerid);
            }
            else if(strlen(inputtext) == 0)
            {
                SendClientMessage(playerid, COLOR_SYSTEM, "You must input the password to your account! If this is not your account, come back with a new name!");
                ShowPlayerDialog(playerid, 1, DIALOG_STYLE_INPUT, "Login / Authentication Process", "Hello there!\n\nPlease enter your password to authenticate.", "Login", "Cancel");
            }
            else
            {
                new buf[129];
                GetFromAccount(PlayerStatistics[playerid][pDatabaseID], "Password", PlayerStatistics[playerid][pPassword]);
                WP_Hash(buf, sizeof (buf), inputtext);
                if(!strcmp(buf, PlayerStatistics[playerid][pPassword], true))
                {
                    PlayerStatistics[playerid][pAuth] = 1;
                    LoadAccountVariables(playerid);

                    format(string, sizeof(string), "You have successfully logged in, %s!", GetName(playerid));
                    SendClientMessage(playerid, COLOR_ORANGE, string);

                    SetPlayerMoney(playerid, PlayerStatistics[playerid][pMoney]);
                    SetPlayerScore(playerid, PlayerStatistics[playerid][pScore]);

                    format(string, sizeof(string), "%s (%d)\n Score: %i", GetName(playerid), playerid, GetPlayerScore(playerid));
                    pNameTag[playerid] = Create3DTextLabel(string, COLOR_YELLOW, 30.0, 40.0, 50.0, 15.0, -1, 1);
                    Attach3DTextLabelToPlayer(pNameTag[playerid], playerid, 0.0, 0.0, 0.2);
                }
                else
                {
                    SendClientMessage(playerid, COLOR_WHITE, "Incorrect password. Please try again!");
                    ShowPlayerDialog(playerid, 1, DIALOG_STYLE_INPUT, "Login / Authentication Process", "Hello there!\n\nPlease enter your password to authenticate.", "Login", "Cancel");
                }
            }
        }
        case 2:
        {
            if(!response)  // If the player hit "exit" we're going to kick them
            {
                SendClientMessage(playerid, COLOR_SYSTEM, "You selected exit, therfore you have been kicked!");
                Kick(playerid);
            }
            else if(strlen(inputtext) < 4 || strlen(inputtext) > 30)
            {
                SendClientMessage(playerid, COLOR_SYSTEM, "Your password must be at least 4, but less than 30 alhpanumeric characters.");
                ShowPlayerDialog(playerid, 2, DIALOG_STYLE_INPUT, "Registration Process", "Hello there!\n\nPlease enter a password to register.", "Authenticate", "Cancel");
            }
            else
            {
                new buf[130], EscapedName[MAX_PLAYER_NAME];
                mysql_real_escape_string(GetName(playerid), EscapedName);
                WP_Hash(buf, sizeof (buf), inputtext);

                format(Query, sizeof(Query), "INSERT INTO `Accounts` (Username, Password) VALUES('%s', '%s')", EscapedName, buf);
                mysql_query(Query);

                JustRegistered = 1;
                PlayerStatistics[playerid][pAuth] = 1;

                format(string, sizeof(string), "You have automatically logged in, %s!", GetName(playerid));
                SendClientMessage(playerid, COLOR_ORANGE, string);

                SpawnPlayer(playerid);
            }
        }
    }
}

public OnPlayerClickPlayer(playerid, clickedplayerid, source)
{
    return 1;
}

// -------------------- [MySQL Stocks and Publics] ------------------------ //

stock ResetPlayerVariables(playerid)
{
    PlayerStatistics[playerid][pDatabaseID] = 0;
    PlayerStatistics[playerid][pAdminLevel] = 0;
    PlayerStatistics[playerid][pMoney] = 0;
    PlayerStatistics[playerid][pAuth] = 0;
    PlayerStatistics[playerid][pPositionX] = 0.00;
    PlayerStatistics[playerid][pPositionY] = 0.00;
    PlayerStatistics[playerid][pPositionZ] = 0.00;
    return 1;
}

stock InitPlayerConnection(playerid)
{
    ResetPlayerVariables(playerid);
    new EscapedName[MAX_PLAYER_NAME];

    mysql_real_escape_string(GetName(playerid), EscapedName);

    format(Query, sizeof(Query), "SELECT `UserID` FROM `Accounts` WHERE `Username` = '%s'", EscapedName);
    mysql_query(Query);
    mysql_store_result();

    if(mysql_num_rows() >= 1)
    {
        if(mysql_num_rows() >= 2)
        {
            mysql_free_result();
            SendClientMessage(playerid, COLOR_WHITE, "There seems to be duplicates of your account, please contact a high-level admin.");
            Kick(playerid);
        }
        else
        {
            PlayerStatistics[playerid][pDatabaseID] = mysql_fetch_int();
            mysql_free_result();

            ShowPlayerDialog(playerid, 1, DIALOG_STYLE_INPUT, "Login / Authentication Process", "Hello there!\n\nPlease enter your password to authenticate.", "Login", "Cancel");
            SendClientMessage(playerid, COLOR_WHITE, "Your account exists. Please enter your password to proceed.");
        }
    }
    else
    {
        mysql_free_result();
        SendClientMessage(playerid, COLOR_WHITE, "Your account does not yet exist. Enter a password to register one!");
        ShowPlayerDialog(playerid, 2, DIALOG_STYLE_INPUT, "Registration Process", "Hello there!\n\nPlease enter a password to register.", "Register", "Cancel");
    }
}

stock SavePlayerAccount(playerid)
{
    if(PlayerStatistics[playerid][pAuth] == 1)
    {
        PlayerStatistics[playerid][pScore] = GetPlayerScore(playerid);
        PlayerStatistics[playerid][pMoney] = GetPlayerMoney(playerid);
        PlayerStatistics[playerid][pSkin] = GetPlayerSkin(playerid);
        format(Query, sizeof(Query), "UPDATE `Accounts` SET `Password` = '%s', `AdminLevel` = '%d', `AdminDuty` = '%d', `Money` = '%d', `Score` = '%d', `Skin` = '%d' WHERE `UserID` = '%d'", PlayerStatistics[playerid][pPassword], PlayerStatistics[playerid][pAdminLevel], PlayerStatistics[playerid][pAdminDuty], PlayerStatistics[playerid][pMoney], PlayerStatistics[playerid][pScore], PlayerStatistics[playerid][pSkin], PlayerStatistics[playerid][pDatabaseID]);
        mysql_query(Query);

        GetPlayerPos(playerid, PlayerStatistics[playerid][pPositionX], PlayerStatistics[playerid][pPositionY], PlayerStatistics[playerid][pPositionZ]);
        format(Query, sizeof(Query), "UPDATE `Accounts` SET `PositionX` = '%f', `PositionY` = '%f', `PositionZ` = '%f' WHERE `UserID` = '%d'", PlayerStatistics[playerid][pPositionX], PlayerStatistics[playerid][pPositionY], PlayerStatistics[playerid][pPositionZ], PlayerStatistics[playerid][pDatabaseID]);
        mysql_query(Query);
    }
    return 1;
}

stock LoadAccountVariables(playerid)
{
    if(IsPlayerConnected(playerid))
    {
        format(Query, sizeof(Query), "SELECT * FROM `Accounts` WHERE `UserID` = %d", PlayerStatistics[playerid][pDatabaseID]);
        mysql_query(Query);
        mysql_store_result();
        mysql_fetch_row(Query, "|");
        sscanf(Query, "e<p<|>ds[23]s[129]dddddfff>", PlayerStatistics[playerid]);
        SpawnPlayer(playerid);
    }
    else
    {
        printf("[MySQL ERROR] LoadAccountVariables() was called, but to a non-connected ID.", playerid);
    }
    mysql_free_result();
}

stock GetFromAccount(dbid, obtaining[], holdingvar[])
{
    format(Query, sizeof(Query), "SELECT `%s` FROM `Accounts` WHERE `UserID` = '%d'", obtaining, dbid);
    mysql_query(Query);
    mysql_store_result();
    if(mysql_fetch_row(holdingvar) == 1)
    {
        mysql_free_result();
    }
    return 1;
}