[Emmet_]

You forgot to store and free the result, therefore mysql_num_rows returned -1 because no result was stored and the function couldn't retrieve any data.

Try this instead:

pawn Код:

CMD:checkregistered(playerid,params[])
{
    new totalreg;
    mysql_query("SELECT COUNT(*) FROM accounts");
    mysql_store_result(); // IMPORTANT
    totalreg = mysql_num_rows();
    mysql_free_result();
    format(str,sizeof(str),"%d has registered on the server.",totalreg);
    SCM(playerid,lightgreen,str);
    return 1;
}