[Calabresi]

Try this:

pawn Code:

public CheckAccount(playerid, account[])
{
    new rows, fields;
    cache_get_data(rows, fields);
    if(rows)
    {
        SetPVarInt(playerid, "IsRegistered", 1); // Then we set PVar for players that are registered already
        ShowPlayerDialog(playerid, DIALOG_LOGIN, DIALOG_STYLE_PASSWORD...);
    }
    return 1;
}

As Vince said, no need to use mysql_num_rows() in R7.