[Logic_]

Use MySQL wildcards and here's how your code should look like:

You can use some wildcard magic to detect similar IPs.

PHP Code:

mysql_format(mysql, query, sizeof query, "SELECT * FROM `accounts` WHERE `IP` = '%s'", PlayerInfo[playerid][p_newIP]);
mysql_pquery(mysql, query, "CheckAKA", "i", playerid); 


PHP Code:

forward CheckAKA(playerid);
public CheckAKA(playerid) {

    new
        rows, ip[18];

    cache_get_row_count(rows);

    for (new i; i < rows; i++) {

        cache_get_value_name(i, "IP", ip);

        if (IpMatch(ip, PlayerInfo[playerid][p_newIP]))
            count ++;
    }

    if (count) {
        format(query, sizeof(query), "[Warning] "white"%s may have connected before to the server with a different name. (/aka %d)", GetName(playerid), playerid);
        
        foreach (new i : Player) {
            if (!PlayerInfo[i][p_Admin])
                continue;

            SendClientMessage(i, COLOR_RED, query);
        }
    }

    return 1;
}