Учебное пособие состоит из двух частей и англо-русского словаря. Материалом для пособия послужило американское издание для изучающих компьютер P. Norton "Introduction to Computers"
жүктеу/скачать 0,7 Mb.
|
| Database Structures
I. Read and translate the text: There are several types of database structures, such as flat-file, relational, hierarchical, network and object-oriented ones. A database that consists of a single data table is called a flat-file (sequential file) database. Flat-file databases are useful for certain single-user or small-group situations, especially for maintaining address lists or inventories. Flat-file database systems are easy to learn and use, but difficult to maintain and limited in their power. When numerous files exist (one for each table or related document), there is often a lot of data redundancy, which increases the chance for errors, wastes time, and uses excess storage space. A relational database is made up of a set of tables, and a common field existing in any two tables creates a relationship between the tables. For example, a Customer ID Number field in both the Customers table and the Orders table links the two tables, while a Product ID field links the Orders and Products tables. The relational database structure is widely used in today's business organizations. In a business, a typical relational database contains such data tables, as Customer information, Employee information, Vendor information, Order information, Inventory information. The hierarchical database is an older style of database. The tables are organized into a fixed treelike structure, with each table storing one type of data. The trunk table (the main table) stores general information. Any field in that table may reference another table that contains subdivisions of data. Each one of those tables may, in turn, reference other tables that store finer subdivisions of data. The relationship between tables is said to be a parent-child relationship, or one-to many relationship, with any child table relating to only one parent table. Each parent table may have many child tables, but each child has only one parent. Hierarchical databases require little duplicated data and may locate data quickly. However, the tables' fixed relationships limit the flexibility of the database, making some kinds of queries or reports difficult or impossible. The network database model is similar to the hierarchical structure except that any one table can relate to any number of other tables. The network database's tables, therefore, are said to have a many-to-many relationship. Like the hierarchical structure, the network database is used in older (primarily mainframe) systems. The object-oriented database (OODB) developed in the late 1980s, groups data items into complex items called objects. These objects can represent anything: a product, an event, a customer complaint, or even a purchase. An object is defined by its characteristics (e.g. text, sound, graphics, video), attributes (e.g. color, size, style, quantity, price), and procedures (the processing associated with an object). Vocabulary: flat-file database ['flxtfail 'deitqbeis] – база данных с последовательным доступом relational database [ri'leiSqnl 'deitqbeis] – реляционная база данных hierarchical database [‚haiq'rRkikql 'deitqbeis] – иерархическая база данных network database ['netwq:k 'deitqbeis] – сетевая база данных object-oriented database ['obGikt 'Lrientid 'deitqbeis] – объектно-ориенти-рованная база данных single ['siNgl] – единственный sequential [si'kwenSql] – последовательный especially [is'peSqli] – особенно to maintain [men'tein] – поддерживать list [list] – перечень, список inventory [in'ventqri] – инвентаризационная опись, товары to learn [lq:n] – изучать difficult ['difikqlt] – трудный to limit ['limit] – ограничивать limited – ограниченный power ['pauq] – мощность, производительность numerous ['nju:mqrqs] – многочисленный data redundancy ['deitq ri'dAndqnsi] – избыточность данных to increase [in'kri:s]– увеличивать, возрастать chance [tSRns] – возможность error ['erq] – ошибка to waste time [weist taim] – тратить время excess [ik'ses] – излишний storage space ['stLriG speis] – объём памяти to be made up (of) [meid'Ap] – быть составленным, состоять (из) any ['eni] – любой anything ['eniTiN]– (всё) что угодно order ['Ldq] – заказ to link [liNk] – связывать, соединять wide [waid] – широкий widely ['waidli] – широко 29. employee [‚emploi'i:] – служащий 30. vendor ['vendq] – поставщик, производитель, продавец 31. treelike ['tri:laik] – древовидный 32. trunk table (main table) [trANk 'teibl] ([mein 'teibl]) – главная (основная) таблица 33. general ['Genqrql]– общий 34. to reference ['refrqns] – ссылаться 35. subdivision ['sAbdi‚viZn] – подраздел, подразделение 36. fine [fain] – мелкий 37. little ['litl] – мало 38. to duplicate ['dju:plikeit] – дублировать, копировать 39. however [hau'evq] – однако, тем не менее 40. flexibility [‚fleksi'biliti] – гибкость 41. impossible [im'posqbl] – невозможный 42. similar (to) ['similq] – аналогичный (чему-л.), сходный (с чем-л.) 43. except (that) [ik'sept] – за исключением (того, что) 44. like [laik] – как, подобно 45. mainframe ['meinfreim] – большой компьютер, мэйнфрейм 46. to develop [di'velqp] – разрабатывать 47. data item ['deitq 'aitqm] – элемент данных 48. event [i'vent] – событие 49. complaint [kqm'pleint] – жалоба 50. purchase ['pq:tSqs] – покупка 51. to define [di'fain] – определять, описывать 52. quantity ['kwontiti] – количество 53. price [prais] – цена 54. procedure [prq'si:Gq] – процедура 55. to associate [q'squSieit] – соединять, связывать II. Answer the questions: What types of database structures are there? What is a flat-file database? Where are flat-file databases used? What are the drawbacks of flat-file databases? What is the structure of a relational database? What tables can a relational database contain? How are the tables in a hierarchical database organized? What information does the trunk table store? What is the relationship between tables in a hierarchical database? What are the advantages and drawbacks of a hierarchical database? What does the network database structure differ from the hierarchical database model in? What kind of systems are the network and hierarchical databases used in? When was the object-oriented database developed? What does it group data items into? What can the objects represent? What is an object defined by? III. Tell whether the following statements are true or false: If a database file contains only one data table, it is called an informational database. Flat-file database systems are difficult to learn and use. A relational database is made up of two tables. In a relational database, a common field existing in any two tables creates a relationship between the tables. A parent-child relationship is the same (то же самое) as a one-to-many relationship. Network databases and hierarchical databases function in the same way (способ). In an object-oriented database, items of data are grouped into complex objects. In an object-oriented database, each object can have only one characteristic. IV. Fill in the blanks: Older database systems that used only a single table are called _________________. In an object-oriented database, an object is defined by its ________________, ________________, and _______________. There are several types of database structures, such as _______, _______, _______, _______and _______ones. Flat-file database systems are _________ in their power. A_________ is made up of a set of tables, and a common field existing in any two tables creates a _________ between the tables. In a hierarchical database the tables are organized into a fixed ________ structure. The network database's tables have a _________ relationship. The relationship between tables in a hierarchical database is called a _________ relationship. V. Choose the right answer: 1. In flat-file databases with numerous files, a common problem is a. Data redundancy c. Disk space restrictions (ограничения) b. Data entry errors d. All the above “Sequential file database” is another term for Hierarchical database c. Network database Flat-file database d. Relational database If a database allows any table to have a relationship with any other table, the tables are said to have One-to-many relationship c. Many-to-one relationship Parent-child relationship d. Many-to-many relationship If a database is made up of a set of tables, it is called Flat-file database c. Relational database Sequential database d. Network database Which of the following kinds of database structure is most widely used in organizations today? Flat-file database c. Sequential database b. Relational database d. Hierarchical database In an object-oriented database, an object can be used to represent Characteristics c. Procedures Nothing d. Anything VI. Match each item to the correct statement below: Flat-file database d. Hierarchical database Relational database e. Network database Object f. Attribute Same as a sequential database. Uses only one table. Uses a set of tables. Its tables have a one-to many relationship. Its tables have a many-to-many relationship. Has characteristics and attributes. Similar to the hierarchical structure. Used in older systems. An object has it. Used for maintaining address lists or inventories. Widely used in business organizations. Characterized by procedures. Speak on the contents of the text using the following chart: жүктеу/скачать 0,7 Mb. Достарыңызбен бөлісу:
|