[Keyhead]

pawn Code:

public OnPlayerConnect(playerid)
{
        GetPlayerIp(playerid, pInfo[playerid][pIP], 16);
}

Then save it.

pawn Code:

stock MySQL_Save(playerid) 
{    
new query[3000];    format(query, sizeof(query), "UPDATE `playerdata` SET ip = '%s', adminlevel = '%d' WHERE username = '%s'",  
pInfo[playerid][pIP],
PlayerData[playerid][pAdminLevel],    
GetPlayerNameEx(playerid));    
mysql_query(query);   
 return 1;
}

Make sure you define the IP Variable.

EDIT:

Why is your query 3000?