public bool Delete(Object obj)
        {
            bool returnResult = false;

            if (obj is Transaction)
            {
                Transaction castObj = (Transaction)obj;
                string      sql     = "DELETE FROM TRANSACTION_TABLE WHERE TRANSACTION_INDEX = " + castObj.Index;
                returnResult = excuteQuery(sql);
                // 해당 거래명의 인덱스를 가진 값은 모두 삭제
                sql          = "DELETE FROM COST_ITEM_TABLE WHERE TRANSACTION_INDEX = " + castObj.Index;
                returnResult = excuteQuery(sql);
            }
            else if (obj is CostItem)
            {
                CostItem castObj = (CostItem)obj;
                string   sql     = "DELETE FROM COST_ITEM_TABLE WHERE COST_ITEM_INDEX = " + castObj.CostItemIndex;
                returnResult = excuteQuery(sql);
            }
            else if (obj is User)
            {
                User   castObj = (User)obj;
                string sql     = "DELETE FROM TRANSACTION_USER_TABLE WHERE USER_ID = '" + castObj.Id + "'";
                returnResult = excuteQuery(sql);
            }

            getAllTables();

            return(returnResult);
        }
        public bool Update(Object obj)
        {
            bool returnResult = false;

            if (obj is Transaction)
            {
                Transaction castObj = (Transaction)obj;
                if (isRowExist(castObj.Index, 0))
                {
                    string sql = "UPDATE TRANSACTION_TABLE SET CUSTOMER_NAME = '" + castObj.CustomerName + "', TRANSACTION_NAME = '" + castObj.TransactionName + "', TRANSACTION_DATE = '" + castObj.TransactionDate + "', SUPPLY_PRICE = " + castObj.SupplyPrice + ", TRANSACTION_CODE = '" + castObj.TransactionCode + "' WHERE TRANSACTION_INDEX =" + castObj.Index;
                    returnResult = excuteQuery(sql);
                }
            }
            else if (obj is CostItem)
            {
                CostItem castObj = (CostItem)obj;
                if (isRowExist(castObj.CostItemIndex, 1))
                {
                    string sql = "UPDATE COST_ITEM_TABLE SET SUPPLIER = '" + castObj.Supplier + "', SUM = " + castObj.Sum + ", NOTE = '" + castObj.Note + "' WHERE COST_ITEM_INDEX =" + castObj.CostItemIndex;
                    returnResult = excuteQuery(sql);
                }
            }
            else if (obj is User)
            {
                User   castObj = (User)obj;
                string sql     = "UPDATE TRANSACTION_USER_TABLE SET USER_PASSWORD = '******', USER_AUTHORITY = " + castObj.Authority + ", DEPARTMENT = " + castObj.Department + "WHERE USER_ID = '" + castObj.Id + "'";
                returnResult = excuteQuery(sql);
            }

            getAllTables();

            return(returnResult);
        }
        public bool Insert(Object obj)
        {
            bool returnResult = false;

            if (obj is Transaction)
            {
                Transaction castObj = (Transaction)obj;
                string      sql     = "INSERT INTO TRANSACTION_TABLE VALUES (" + castObj.Index + ", '" + castObj.CustomerName + "', '" + castObj.TransactionName + "', '" + castObj.TransactionDate + "', " + castObj.SupplyPrice + ", " + castObj.Department + ", '" + castObj.TransactionCode + "')";
                returnResult = excuteQuery(sql);
            }
            else if (obj is CostItem)
            {
                CostItem castObj = (CostItem)obj;
                string   sql     = "INSERT INTO COST_ITEM_TABLE VALUES  (" + castObj.CostItemIndex + ", " + castObj.TransactionIndex + ", '" + castObj.Supplier + "', '" + castObj.Sum + "', NULL, NULL, NULL, '" + castObj.Note + "')";
                returnResult = excuteQuery(sql);
            }
            else if (obj is User)
            {
                User   castObj = (User)obj;
                string sql     = "INSERT INTO TRANSACTION_USER_TABLE VALUES ('" + castObj.Id + "', '" + castObj.Password + "', " + castObj.Authority + ", " + castObj.Department + ", 'logout')";
                returnResult = excuteQuery(sql);
            }

            getAllTables();

            return(returnResult);
        }