[Calisthenics]

The problem is no active cache. You need to retrieve insert id in a specified callback of `mysql_tquery` function.

Extra notes:

pawn Код:

mysql_format(Database, query, sizeof(query), "SELECT * FROM `clans` WHERE `ClanName` = '%e'", clanname);

Why do you select everything? A better method would be using COUNT(*) which returns 1 row and 1 column (0 or 1 in your case). An even better method is just 1 INSERT query.

Set `ClanName` column as UNIQUE KEY. Now you execute normally your query with `IGNORE` keyword:

pawn Код:

mysql_format(Database, query, sizeof(query), "INSERT IGNORE INTO `clans` (`ClanName`, `ClanLeader`, `Official`) VALUES ('%e', '%e', '0')", clanname, GetName(playerid)); 
mysql_tquery(Database, query, "OnClanCreate", "ds", playerid, clanname);

You can set `Official` as default value 0 in table structure too.

It will execute the query and affected rows will be:
0) a clan with this name exists
1) all is OK, new row was inserted.

pawn Код:

forward OnClanCreate(playerid, clanname[]);
public OnClanCreate(playerid, clanname[])
{
    if (cache_affected_rows())
    {
        new clanid = UserStats[playerid][Clan] = cache_insert_id(); 
        ...
    }
    else
    {
        SendClientMessageEx(playerid, COLOR_RED, "[ERROR]: Clan name ''%s'' already exists. Pick another name.", clanname); 
    }
}

Do not copy strings directly like this:

pawn Код:

ClanInfo[clanid][ClanName] = clanname; 
ClanInfo[clanid][ClanLeader] = GetName(playerid);

use `strcpy` macro.