【導(dǎo)讀】database.Resources(HR)department.information,alsoknownasatable.describesaperson,place,orthing.

　　

【正文】 and access limitations, developers w ho wanted to w ork with SQL Server and Oracle databases generally sought other options. Remote Data Objects Microsoft provided another option in RDO, w hich originally released with Visual Basic 4 Enterprise Edition. RDO39。s o bject model closely resembles the hierarchy of structures in the ODBC API. Programmers found that RDO provided much faster access to client/server database systems, such as SQL Server and Oracle, than DAO did. Although those familiar with the ODBC API quic kly learned how to work with the RDO object model, developers lacking experience with that API, such as those w ho had been using DAO, found the RDO technology difficult to use. The object model itself wasn39。t the problem for most programmers learning RDO: the nuances inherited from the ODBC API posed the greatest obstacles. Suddenly, programmers had to bone up on cursors and bookmarks. They had to learn many of the ins and outs of specific database systems. Does the error message The connection is busy with results from another hstmt ring any bells out there? If you try to do the impossible on an ODBC connection to your database, RDO w on39。t save 重慶理工 大學(xué) 2021 屆本科生畢業(yè)設(shè)計(jì) (論文 )外文文獻(xiàn)翻譯 18 you. Instead, you39。ll get that error. DAO hid the problem from you by automatically creating another connection to your database to perform the action you requested. Another challenge that RDO posed for programmers accustomed to writing DAO code was that RDO lacked many of DAO39。s features, such as sorting, searching, and filtering. Other DAO functionality unavailable in the RDO w orld includes data definition language (DDL) interfaces to ODBC API functions such as Create Table and Create Field. Best of Both Worlds: ActiveX Data Objects Programmers clamored for a data access technology that bined the simplicity and rela tive ease of use of DAO w ith the speed, pow er, and control of RDO. Initially introduced as part of the Microsoft Inter Information Server 3 package, ADO was intended to be all things to all people. Of course, such lofty goals are rarely fulfilled. While the initial release of ADO lacked many of Rod’s features, I believe that ADO offered parable functionality. Certain RDO features, such as mixed cursors, have yet to be implemented in ADO, but these features are few and far betw een. In fact, I39。m at a loss to name a single significant feature available in RDO that w as not available in ADO in one form or another. (I39。m sure someone will tell me otherwise。 a great w ay to find such features is to make a statement like that in a book like this.) With the release of version , ADO and its supporting libraries began offering nearly all features available in DAO. DDL libraries w ere added to ADO in version to provide functionality similar to functions available with DAO, such as Create Table, Create F ield, and Create Index. Microsoft Jet and Replication Objects (JRO) in ADO offers much of the Jetspecific functionality available via the DB Engine object in DAO. ADO also added functionality to simplify the 重慶理工 大學(xué) 2021 屆本科生畢業(yè)設(shè)計(jì) (論文 )外文文獻(xiàn)翻譯 19 retrieval of newly generated identity v alues. ADO adds no new functionality to more closely match the capabilities of DAO and RDO, because perhaps the only place w here ADO lags behind DAO is in its searching and filtering capabilities. So ADO has most of the functionality of RDO and DAO as w ell as many helpful features not available in previous data access technologies. Database Management There are problems with traditional data manage ment. A more subtle problem is data dependency. When a problem’s logic is tied to it’s physical data struc ture, changing that structure w ill almost certainly require changing the program. As a result, programs using traditional access methods can be difficult to maintain. The solution to both problems id often anizing the data as a single, integrated databa se. The task of controlling access to all the data can then be concentrated in a centralized database management system. How dose the use of a centralized database solve the data redundancy problem? All data are collected and stored in a single place。 consequently, there is one and only one copy of any given data element. When the value of an element (an address, for example) changes, the single database copy is corrected. Any program requiring access to this data element gets the same value, because there is only one value. How dose a database help to solve the data dependency problem? Since the responsibility for accessing the physical data rests with the database manageme nt system, the programmer can ignore the physical data structure. As a result, progra ms tend to be much less dependent upon their data, and are generally much easier to maintain. Expect the trend tow ard database management to continue. 重慶理工 大學(xué) 2021 屆本科生畢業(yè)設(shè)計(jì) (論文 )外文文獻(xiàn)翻譯 20 重慶理工 大學(xué) 2021 屆本科生畢業(yè)設(shè)計(jì) (論文 )外文文獻(xiàn)翻譯 21 數(shù)據(jù)庫管理系統(tǒng) 來源： 數(shù)據(jù)庫和網(wǎng)絡(luò)雜志 作者：大衛(wèi)安德森 眾所周知，數(shù)據(jù)庫是邏輯上相關(guān)的數(shù)據(jù)源集合。這些數(shù)據(jù)源可以按照不同的結(jié)構(gòu)組織起來，以滿足單位和個(gè)人的多方面的要求。數(shù)據(jù)庫本身并沒有什么新東西 —— 早期的數(shù)據(jù)庫鑿在石頭上，記在名冊上，以及寫在索引卡中。而現(xiàn)在普遍記錄在可磁化的介質(zhì)上，并且需要用計(jì)算機(jī)程序來執(zhí)行必須的存儲(chǔ)和檢索操作。 處理與創(chuàng)建、訪問以及維護(hù)數(shù)據(jù)庫記錄有關(guān)的復(fù)雜任務(wù)的系統(tǒng)軟件包叫做數(shù)據(jù)管理。 DBMS 軟件包中的程序在數(shù)據(jù)庫及其用戶間建立接口（這些用戶可以是應(yīng)用程序員）。 DBMS 可組織、處理和顯示從數(shù)據(jù)庫選擇的數(shù)據(jù)源。該功能可以是決策者搜索、試探和查詢數(shù)據(jù)庫的內(nèi)容，從而對正式報(bào)告中沒有的、不再出現(xiàn)的、且無計(jì)劃的問題做出回答。這些問題最初可能是模糊的并且 /或者是定義拙劣的，但是人們可以瀏覽數(shù) 據(jù)庫知道獲得數(shù)據(jù)的答案。簡言之， DBMS 將“管理”存儲(chǔ)的數(shù)據(jù)項(xiàng)，并從公共數(shù)據(jù)庫中匯集所需的數(shù)據(jù)項(xiàng)來響應(yīng)那些非程序員的詢問。在面向文件的系統(tǒng)中，需要特定的用戶可以將它們的要求傳送給數(shù)據(jù)員，并準(zhǔn)備信息。但是使用 DBMS 可為用戶提供一個(gè)更快的、用戶可選擇的通信方式。 順序 的直接的以及 其它的文件處 理方式通常 用于單個(gè)文件 中的組織和結(jié)構(gòu)，而 DBMS 可綜合多個(gè)文件的數(shù)據(jù)項(xiàng)，并回答某個(gè)用戶對信息的查詢。這意味著 DBMS 能夠訪問和檢索非關(guān)鍵字字段的數(shù)據(jù)，即 DBMS 能夠?qū)讉€(gè)大文件中邏輯相關(guān)的數(shù)據(jù)組織并聯(lián)在一起。 邏輯結(jié)構(gòu) 。確定這些邏輯關(guān)系是數(shù)據(jù)庫管理者的任務(wù)，由數(shù)據(jù)定義語言完成。 DBMS 在存儲(chǔ)、訪問和檢索操作過程中可以選用的邏輯技術(shù)有： 1 表結(jié)構(gòu) 2 層次（樹型）結(jié)構(gòu) 3 網(wǎng)狀結(jié)構(gòu) 4 關(guān)系性結(jié)構(gòu)。 。在該邏輯方式中，記錄通過指針連接在一起。指針是記錄中的一個(gè)數(shù)據(jù)項(xiàng)，它指出另一個(gè)邏輯相關(guān)的記錄的存儲(chǔ)位置。例如，顧客主文件中的記錄將包含每個(gè)顧客的姓名和地址，而且該文件重慶理工 大學(xué) 2