Use database queries in source code?

[Furniture]

Hi, I need to know how to run database queries in my source code. I am trying to remove trade between characters who have different "expansion" values in my character_vars table as I made per here: http://www.eqemulator.net/wiki/wikka...mCharacterData

Here is my code:

void Client::Handle_OP_TradeRequest(const EQApplicationPacket *app)
{
	if (app->size != sizeof(TradeRequest_Struct)) {
		LogFile->write(EQEMuLog::Error, "Wrong size: OP_TradeRequest, size=%i, expected %i", app->size, sizeof(TradeRequest_Struct));
		return;
	}

	
	// Client requesting a trade session from an npc/client
	// Trade session not started until OP_TradeRequestAck is sent

	BreakInvis();

	// Pass trade request on to recipient
	TradeRequest_Struct* msg = (TradeRequest_Struct*) app->pBuffer;
	Mob* tradee = entity_list.GetMob(msg->to_mob_id);



	if (tradee && tradee->IsClient()) { {
		char *query = 0;
    MYSQL_RES *result;
    MYSQL_ROW row;
    char errbuf[MYSQL_ERRMSG_SIZE];
	int myExpansion = -1;
	int tradeeExpansion = -2;
    
    MakeAnyLenString(&query, "SELECT %s FROM character_vars WHERE character_id = %i", expansion, AccountID());
    if (database.RunQuery(query, strlen(query), errbuf, &result))
    {
        safe_delete_array(query);
        row = mysql_fetch_row(result);
        mysql_free_result(result);
         myExpansion = (atoi(row[0]));
	}

		MakeAnyLenString(&query, "SELECT %s FROM character_vars WHERE character_id = %i", expansion, tradee->CastToClient()->AccountID());
    if (database.RunQuery(query, strlen(query), errbuf, &result))
    {
        safe_delete_array(query);
        row = mysql_fetch_row(result);
        mysql_free_result(result);
         tradeeExpansion = (atoi(row[0]));
	}

	if (myExpansion != tradeeExpansion)
	{
		return;
	}

	


    

	
	

		
		tradee->CastToClient()->QueuePacket(app);
	}

This compiles fine but crashes the zone when a trade initiates. Can anybody help me fix this or even know if there is an easier way I could do this?