Task 2. Match the meaning of the following English words with the Ukrainian equivalents.
UNIT 21
DATABASES
Vocabulary Bank Unit 21
Task 1. Read, write the translation and learn the basic vocabulary terms:
1. indexed filing cabinet
2. averaging
3. background
4. bearing (n)
5. BLOB (binary large objects)
6. Boolean data
7. card index system
8. challenging task
9. commission field
10. consistent position
11. conversion routine
12. decision making
13. enormous
14. envision
15. essential
16. export routine
17. extensive
18. fixed-length
19. flexibly
20. fluency
21. inaccurate
22. integer
23. intricacy
24. invoice
25. joining table
26. lookup
27. manual filing system
28. meaningful
29. merging
30. messy
31. pay check
32. percentage
33. perspective
34. redundancy
35. relational database
36. sophisticated query language
37. SQL (structured query language)
38. table’s sort key
39. term parameter
40. timely
41. to accomplish
42. to compile
43. to concise
44. to contain
45. to delineate
46. to prevent
47. to retrieve
48. to specify
49. to stand for
50. to think ahead
51. treatment
52. user-defined
53. validation rule
54. validity
55. variable-length
56. well-defined
Text 21 A. DATABASE DESIGN
With a database you can store, organize and retrieve a large collection of related information on computer. If you like, it is the electronic equivalent of an indexed filing cabinet. Let us look at some features and applications.
Information is entered into the database via fields. Each field holds a separate piece of information, and the fields are collected together into records. For example, a record about an employee might consist of several fields which give their name, address, telephone number, age, salary and length of employment with the company. Records are grouped together into files which hold large amounts of information. Files can easily be updated: you can always change fields, add new records or delete old ones. With the right database software, you are able to keep track of stock, sales, market trends, orders, invoices and many more details that can make your company successful.
Another feature of database programs is that you can automatically look up and find records containing particular information. You can also search on more than one field at a time. For example, if a managing director wanted to know all the customers who spend more than $ 17,000 per month, the program would search on the name field and the money field simultaneously.
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A computer database is much faster to consult and update than a card index system. It occupies a lot less space, and records can be automatically sorted into numerical or alphabetical order using any field.
The best packages also include networking facilities which add a new dimension of productivity to businesses. For example, managers of different departments can have direct access to a common database, which represents an enormous advantage. Thanks to security devices, you can share a part of your files on a network and control who sees the information. Most aspects of the program can be protected by user-defined passwords. For example, if you wanted to share employee’s personal details, but not their commission, you could protect the commission field. In short, a database manager helps you control the data you have at home, in the library or in your business.
The key to an effective database is its initial design. In a well-designed database, data can be flexibly manipulated to produce timely, meaningful, and accurate information for decision making. A bad database design can lead to messy database, lost records, and inaccurate data. The goal of a database design is to store information so that it is easy to access and maintain, but concise enough to take up as little disk space as possible.
The term database structure refers to the arrangement of fields, tables, and relationships in a database. The first step in structuring a relational database is to determine what data must be collected and stored. To do so, a database designer might start with consulting users and studying the current filing system to compile a list of available data as well as any additional data necessary to produce on-screen output or printed reports.
After the designer determines what data to store, the next step is to organize that data into fields. It is usually easy to break data into fields just by using common sense and considering how people might want to access the data. Any data that people would search for, sort on, or use in a calculation should be in its own field. The treatment of the first and last name illustrates the concept of breaking data into fields. A database designer could define a field called Name to hold an entire customer’s name.
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With the entire name in one field, however, the database would not be able to access individual parts of the name, making it difficult to alphabetize customers by the last name or to produce a report in which names appear in one field. That’s why the last names are stored in a different field than the first names.
Although two people might have, for example, the same name or two paychecks might contain the same amount, a computer must have some way to differentiate between records. A primary key is a field that contains data unique to a record.
The data that can be entered into a field depends on the field’s data type. From a technical perspective, a data type specifies the way the data is represented on the disk and in RAM. From a user perspective, the data type determines the way data can be manipulated. When designing a database, each field is assigned a data type. Data can be broadly classified as numeric or character. Character data contains letters, numerals and symbols not used for calculations. Numeric data contains numbers that can be manipulated mathematically by adding, averaging, multiplying and so forth. There are several numeric data types, including real, integer, and date. The real data type is used for fields that contain numbers with decimal places- prices, percentages, and so on. The integer data type is used for fields that contain whole numbers-quantities, repetitions, rankings, and so on. The date data type is used to store dates in a format that allows them to be manipulated, such as you want to calculate the numbers of days between two dates.
The text data type is typically assigned to fixed-length fields that hold character data- people’s names, albums titles, and so on. Text fields sometimes hold data that looks like numbers, but doesn’t need to be mathematically manipulated. Telephone numbers and ZIP codes are examples of the data that looks numeric, but should be stored in text fields. A memo data type usually provides a variable-length field into which users can enter comments. The logical data type (sometimes called a Boolean or yes/no data type) is used for true/false or yes/no data using minimal storage space. Some file and database management systems also include additional data types, such as BLOBs and hyperlinks. A BLOB (binary large object) is a collection of binary data stored in a single field of a database. BLOBs can be just about any kind of data you would store as a file, such as an MP3 music track. The hyperlink data type stores URLs used to link directly from a database to a Web page.
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The information produced by reports and processing routines is only as accurate as the information in the database. Unfortunately, data entry errors can compromise the accuracy and validity of a database. When designing a database, it is important to think ahead and envision potential data entry errors. Preventing every typographical error is not possible. However, it is possible to catch some of these errors by using field validation rules, list boxes, or lookups. A process called normalization helps to create a database structure that can save storage space and increase processing efficiency. The goal of normalization is to minimize data redundancy – the amount of data that is repeated or duplicated in a database.
Records in a database can be organized in different way depending on how people want to use them. No single way of organizing the data accommodates everyone’s needs, but tables can be sorted or indexed in multiple ways. A table’s sort order is the order in which records are stored on a disk. Sorted tables typically produce faster queries and updates. In a sorted table, new records are inserted to maintain the order. Most DBMSs use a sort key to determine the order in which records are stored. A table’s sort key is one or more fields used to specify where new records are inserted in a table. A database index can be used to organize data in alphabetic or numeric order. A database index contains a list of keys, and each key provides a pointer to the record that contains the rest of the fields related to that key.
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Designing the database user interface can be a challenging task. If a company’s database includes multiple tables used by many different people, a professional user interface designer usually creates and maintains the user interface. Large databases might even require a group of user interface designers, meanwhile the interfaces for smaller databases, such as those used by small business or individuals, is most likely created by a single one.
A well-defined user interface for a database should be clear, intuitive, and efficient. A designer might consider the following principles:
Arrange fields in a logical order beginning at the top-left of the screen. The first field should be those used most often or those that come first in the data entry sequence.
Provide visual clues to the entry areas. An edit box, line, or shaded area can delineate data entry areas.
Entry areas should appear in a consistent position relative to their labels. By convention, labels are placed left of the entry areas or above them.
Provide a quick way to move through the fields in order. By convention, the tab key performs this function.
If all fields do not fit on a single screen, use scrolling or create a second screen.
Provide buttons or other easy-to-use controls for moving from one record to another.
Supply on-screen instructions to help ensure that data is entered correctly. Web database can benefit from links to help pages.
After the design for the database structure is completed, it is time to load the database with an initial set of data. Data can be loaded into a database manually by using generic data entry tools supplied with the DBMS or by using a customized data entry module created by a database designer. Entering data manually can take a long time, however, and mistakes such as misspelling are common. If the data exists electronically in another type of a database or in flat files, it is usually possible to transfer the data using a custom-written conversion routine or import and export routines. A conversion routine converts the data from its current format into a format that can be automatically incorporate into a new database. It takes some time and requires knowledge about database formats to write conversion routines, but for large databases, it’s much quicker to convert data than to re-enter it manually. Converting data also results in fewer errors.
Some DBMSs provide built-in import and export routines that automatically convert data from one file format to another. An import routine brings data into a database. For example, if data was previously stored as a spread-sheet file, an import routine in Microsoft Access can be used to transfer data from the spreadsheet to an Access database. In contrast, an export routine copies data out of a software package, such as spreadsheet software, and transfers it into the database. Typically, you would use either an import routine or an export routine to move data from one location to another, but not both.
Task 2. Match the meaning of the following English words with the Ukrainian equivalents.
1. conversion routine а) надмірність даних
2. data redundancy b) порядок сортування
3. BLOB c) індекс бази даних
4. variable-length field d) конверсійна програма
5. primary key e) первинний ключ
6. sort order f) цілочисельний тип даних
7. validation rule g) великий двійковий об’єкт
8. fixed-length field h) поле нерухомої довжини
9. integer data type i) правило ратифікації
10. database index j) поле змінної довжини
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