Chapter 11 Database Management 11.I Overview Database records and files must be organized to allow retrieval of the information. Early systems were arranged sequentially (i. e, alphabetically, numerically, or chronologically); the development of direct-access storage devices made possible random access to data via indexes. Queries are the main way users retrieve data base information. Typically, the user provides a string of characters, and the computer searches the data base for a corresponding sequence and provides the source materials in which those characters appear. a user can request, for example, all records in which the content of the field for a persons last name is the word Smith 数据库记录和文件的组织必须确保能对信息进行检索。早期的系统是顺序 组织的(如:字母顺序、数字顺序或时间顺序);直接访问存储设备的研 制成功使得通过索引随机访问数据成为可能。用户检索数据库信息的主要 方法是 query(查询)。通常情况下,用户提供一个字符串,计算机在数据 库中寻找相应的字符序列,并且给出字符串在何处出现。比如,用户能够 在所有记录中寻找所有 Tlast name域为 Smith的记录 计算机专些英语 11-6
Chapter 11 Database Management 计算机专业英语 11-6 11.1 Overview Database records and files must be organized to allow retrieval of the information. Early systems were arranged sequentially (i.e., alphabetically, numerically, or chronologically); the development of direct-access storage devices made possible random access to data via indexes. Queries are the main way users retrieve database information. Typically, the user provides a string of characters, and the computer searches the database for a corresponding sequence and provides the source materials in which those characters appear. A user can request, for example, all records in which the content of the field for a person’slast name is the word Smith. 数据库记录和文件的组织必须确保能对信息进行检索。早期的系统是顺序 组织的（如：字母顺序、数字顺序或时间顺序）；直接访问存储设备的研 制成功使得通过索引随机访问数据成为可能。用户检索数据库信息的主要 方法是query(查询)。通常情况下，用户提供一个字符串，计算机在数据 库中寻找相应的字符序列，并且给出字符串在何处出现。比如，用户能够 在所有记录中寻找所有last name域为Smith的记录
Chapter 11 Database Management 11.1 Overview In flat databases 21, records are organized according to a simple list of entities; many simple data bases for personal computers are flat in structure. The records in hierarchical data bases are organized in a treelike structure, with each level of records branching off into a set of smaller categories. Unlike hierarchical databases, which provide single links between sets of records at dififerent levels network databases create multiple linkages between sets by placing links, or pointers, to one set of records in another; the speed and versatility of network data bases have led to their wide use in business 在非结构化的数据库中,按照实体的一个简单列表组织记录;很多个人 计算机的简易数据库是非结构的。层次型数据库按树型组织记录,每 层的记录分解成更小的属性集。层次型数据库在不同层的记录集之间提 供一个单一链接,与此不同,网络型数据库在不同记录集之间提供多个 链接,这是通过设置指向其它记录集的链或指针来实现的。网络型数据 库的速度及多样性使其在企业中得到广泛应用。 雾语1
Chapter 11 Database Management 计算机专业英语 11-7 In flat databases [2] , records are organized according to a simple list of entities; many simple databases for personal computers are flat in structure. The records in hierarchical databases are organized in a treelike structure, with each level of records branching off into a set of smaller categories. Unlike hierarchical databases, which provide single links between sets of records at different levels, network databases create multiple linkages between sets by placing links, or pointers, to one set of records in another; the speed and versatility of network databases have led to their wide use in business. 在非结构化的数据库中，按照实体的一个简单列表组织记录；很多个人 计算机的简易数据库是非结构的。层次型数据库按树型组织记录，每一 层的记录分解成更小的属性集。层次型数据库在不同层的记录集之间提 供一个单一链接，与此不同，网络型数据库在不同记录集之间提供多个 链接，这是通过设置指向其它记录集的链或指针来实现的。网络型数据 库的速度及多样性使其在企业中得到广泛应用。 11.1 Overview
Chapter 11 Database Management 11.1 Overview Relational data bases are used where associations among files or records cannot be expressed by links; a simple flat list becomes one table, or "relation", and multiple relations can be mathematically associated to yield desired information. Object-oriented databases store and manipulate more complex data structures, called objects", which are organized into hierarchical classes that may inherit properties from classes higher in the chain; this data base structure is the most flexible and adaptable 当文件或记录间的关系不能用链表达时,使用关系型数据库。 个表或一个“关系”,就是一个简单的非结构列表。多个关系可 通过数学关系提供所需信息。面向对象的数据库存储并处理更复 杂的称为对象的数据结构,可组织成有层次的类,其中的每个类 可以继承层次链中更高一级类的特性,这种数据库结构最灵活 最具适应性。 《什第机专出美语 18
Chapter 11 Database Management 计算机专业英语 11-8 Relational databases are used where associations among files or records cannot be expressed by links; a simple flat list becomes one table, or “relation”, and multiple relations can be mathematically associated to yield desired information. Object-oriented databases store and manipulate more complex data structures, called “objects”, which are organized into hierarchical classes that may inherit properties from classes higher in the chain; this database structure is the most flexible and adaptable. 当文件或记录间的关系不能用链表达时，使用关系型数据库。一 个表或一个“关系” ，就是一个简单的非结构列表。多个关系可 通过数学关系提供所需信息。面向对象的数据库存储并处理更复 杂的称为对象的数据结构，可组织成有层次的类，其中的每个类 可以继承层次链中更高一级类的特性，这种数据库结构最灵活， 最具适应性。 11.1 Overview