讲述计算机DBMS的编排技巧的英语

计算机英语 sequential 顺序的，连续的 integrate 综合，使成整体 access v. 访问 retrieve v.找回，检索 employ v.使用 list structure n.链表结构 invoice n. 发票 pointer n.指针 hierarchical structure 树结构 subordinate adj. 从属的 network structure 网状结构 relational structure 关系结构 physical structure 物理结构 Abbreviations: DBMS(Database Management System) 数据库管理信息系统 DBMS is able to access and retrieve data from nonkey record fields. That is, the DBMS is able to structure and tie together the logically related data from several large files. DBMS 可综合几个文件的数据项以回答用户对信息的查询，这就意味着 DBMS 能够访问和检索非关键记录字段的数据，即 DBMS 能够将几个大文件 中逻辑相关的数据组织并连接在一起。 Logical Structures. Identifying these logical relationships is a job of the data administrator. A data definition language is used for this purpose. The DBMS may then employ one of the following logical structuring techniques during storage access, and retrieval operations [1]: 逻辑结构。确定这些逻辑关系是数据管理者的任务，由数据定义语言完 成。DBMS 在存储、访问和检索操作过程中可选用以下逻辑构造技术: 1. List structures. In this logical approach, records are linked together by the use of pointers. A pointer is a data item in one record that identifies the storage location of another logically related record. Records in a customer master file, for example, will contain the name and address of each customer, and each record in this file is identified by an account number. During an accounting period, a customer may buy a number of items on different days. Thus, the company may maintain an invoice file to reflect these transactions. 链表结构。在该逻辑方式中，记录通过指针链接在一起。指针是记录中 的一个数据项，它指出另一个逻辑相关的记录的存储位置，例如，顾客主文 件中的记录将包含每个顾客的姓名和地址，而且该文件中的每个记录都由一 个账号标识。在记账期间，顾客可在不同时间购买许多东西,公司保存一个发 票文件以反映这些交易。 A list structure could be used in this situation to show the unpaid invoices at any given time. Each record in the customer file would contain a field that would point to the record location of the first invoice for that customer in the invoice file (fig11-1). This invoice record, in turn, would be linked to later invoices for the customer. The last invoice in the chain would be identified by the use of a special character as a pointer. 这种情况下可使用链表结构，以显示给定时间内未支付的发票。顾客文 件中的每个记录都包含这样一个字段，该字段指向发票文件(图 11-1)中该顾 客的第一个发票的记录位置，该发票记录又依次与该顾客的下一个发票记录 相连，此链接的最后一个发票记录由一个作为指针的特殊字符标识。