1. R. E. Wyllys Copyright © 2000 by R. E. Wyllys Last revised 2003 Jun 25
LIS Information Technologies and the Information Professions Introduction to Databases
R. E. Wyllys
Copyright © 2000 by R. E. Wyllys
Last revised 2003 Jun 25
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2. Lesson Objectives You will
Understand the distinctions among flat-file databases (DBs), network DBs, hierarchical DBs, relational DBs, and text-oriented DBs
Become aware that relational DBs have a characteristic known as the level of normalization and that the secret of attaining a satisfactory level of normalization in a DB lies in making its tables simple.
Become aware that modern relational DBs use a standardized language for commands, known as Structured Query Language (SQL)
Understand that multiuser databases face problems of security and privacy
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3. The world is full of files of data and information,
which databases can help you find and manage.
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4. Examples of Databases What does the word "database" mean?
Nowadays we usually think it means a computer-stored set of information
However, databases can exist in many forms. Examples:
Electronic data: text, visual images, audio images, numbers
Sheets of paper in folders in a vertical file
A book (think of it as a collection of sentences and illustrations)
Books in a collection (e.g., a library)
Sets of 3"x5" cards containing notes
Blueprints
Maps and other forms of geographic information systems
Core samples from oil wells
Blood samples in a medical laboratory
DNA samples in a forensic laboratory
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5. Examples of Databases What do these examples have in common?
Sets of data and information composed of, and/or represented by: bits; or alphanumeric symbols; or lines and shapes in drawings, pictures, and maps; or audio recordings; or video recordings; or realia (i.e., actual substances)
At least one means by which the sets of data and information are organized in order to facilitate access to individual desired sets
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6. Examples of Databases
Consider the provisions for access to individual pieces of information in the following examples:
Phone book. Contains a collection of several independent (discrete) databases, each consisting of names together with corresponding phone numbers:
White-pages personal listings, arranged alphabetically by surname and within surname by first names
White-pages corporate listings, arranged alphabetically
Blue-pages governmental listings: primary arrangement alphabetical by type of government (city, county, state, federal), secondary arrangement alphabetical by agency within type of government, tertiary arrangement alphabetical by office within agency
Yellow-pages listings: primary arrangement by type of business, secondary arrangement alphabetically by company within type of business, plus various special groupings (e.g., restaurants by ethnic type)
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7. Examples of Databases
Provisions for access to individual pieces of information, cont'd:
Organizational membership directory, usually consisting of names together with corresponding postal addresses, telephone numbers, and addresses
Typically contains listings by surname and first names, plus groupings by regions (e.g., states, countries) and by membership in special interest groups (SIGs), arranged alphabetically by name within regional groups and SIGs
Dictionary, consisting of words with corresponding definitions, and in some cases, lists of synonyms and/or antonyms
Primary collection is individual words arranged alphabetically
May contain separate sections (e.g., geographical names, biographical names, abbreviations, proofreaders' marks)
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8. Examples of Databases
Provisions for access to individual pieces of information, cont'd:
Thesaurus
Primary arrangement by broad concepts (themes), with subgroupings of sets of closely related words (often arranged by type of speech, e.g., nouns, verbs), each set sharing a subconcept of the primary concept; sometimes includes antonyms of the primary concept and/or selected subconcepts
Book (non-fiction)
Table of contents
Provides access to chapters (and sometimes to subchapters) dealing with broad topics that are aspects of the overall subject(s) of the book
Index
Organizes narrow concepts by names, terms, subterms, etc.
Provides pointers from terms to relevant locations in text of book
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9. Examples of Databases
The foregoing examples illustrate some ways of organizing information in DBs, whether computerized or non-computerized: viz.,
An intrinsic index provides information organized by and with the entry or record; or
A separate index can point to the location of the information; or
Records (i.e., basic packages of information) can contain retrieval tags (access tags, labels, etc.) that identify them and that can be searched for; or
(Worst Case) Records can be sought via exhaustive search (by humans or computer programs)
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10. Computerized Databases
Consist of
Bits, organized into bytes, which in turn are organized into sequences or strings of bytes
Fields: sets of bytes that represent information
Records: sets of fields that are associated by sharing relevance to some entity
Files: sets of records sharing relevance to a particular type of entity
Databases typically consist of one or more sets of related files
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11. Computerized Databases
Of special interest are Relational Databases (RDBs) and programs that manage them, known as Relational Database Management Systems (RDBMSs).
Note: The word "relational" is often omitted nowadays, since almost all well known DBMSs (e.g., IBM DB2, MS Access, MS SQL Server, Oracle, Sybex) are RDBMSs.
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12. Introduction to RDBs
In discussing relational databases, we use synonymously the words
File, table, relation
Record and row
Field, column, attribute
Note: Discussions of RDB theory tend to prefer the words italicized above
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13. Introduction to RDBs Definition:
A relational database is a set of one or more tables that together embody information about a set of related concepts and entities.
If, as is usually the case, a relational database has more than one table, the tables are connected (related) in the following way:
It is possible to move from any one table in the RDB to any other table in the RDB via a chain of columns (i.e., fields, attributes) shared in pairwise fashion by successive tables.
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14. Introduction to RDBs
The picture below shows 3 tables, with a total of 12 attributes (i.e., 12 distinct columns). The top and middle tables share Attribute 3; the middle and bottom tables share Attribute 7.
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15. Database Applications
The word "application" has a special technical meaning in the field of database management.
Definition:
A database application is a combination of
A relational database-management system (RDBMS)
A relational database (RDB)
Associated menus, data-entry forms, and report forms
Documentation (e.g., manuals) for the users.
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16. Database Applications
A database application is a package designed to facilitate a particular real-world function (or a set of related functions): e.g., looking up books in a library catalog, or handling a sales transaction in a store.
Note: An application may include more than one RDB, and/or it may include a "stray" table or two, so long as such additions serve the basic function and make the whole package more convenient for humans to use.
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17. Other Types of DBs Types of Databases (other than RDBs)
Flat-file (spreadsheet)
Hierarchical
Network
Text-oriented
Geographic information systems
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18. Flat File DBs
Flat-file DBs are like the DBs you can construct in a spreadsheet, i.e., all the information in the DB is in one file consisting of one array of rows and columns. For example:
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19. Flat File DBs Flat-file databases (spreadsheet style) Advantages
Simple
Suitable for small numbers of records with few attributes
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20. Flat File DBs Flat-file databases (spreadsheet style) Disadvantages
Likely to include repetitions of data
Multi-valued attributes (e.g., multiple authors, multiple phone numbers) require repetitions of accompanying data (see the "Fulano" entries in the example below)
Changes in data are difficult to implement
Deletion and insertion anomalies are common
Often lead to too much information in one table
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21. Hierarchical DBs Hierarchical databases
Are based on a classification scheme (a taxonomy). Any element (node) in the database is linked only to the elements directly above it and directly below it.
Typically require custom programming
The original computer-based databases were designed for banking. Hierarchical databases were appropriate for such purposes: e.g., individual accounts can be grouped by family or business; sets of accounts, grouped by branch; accounts in different branches, grouped by city; accounts in different cities, grouped by state.
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22. Hierarchical DBs
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23. Network DBs Network databases
Permit links among all components, without restrictions to hierarchical levels; i.e., elements can be linked to other elements anywhere in the database, not just those directly above and below
Can be extremely difficult to manage
The World-Wide Web is a very large example of a network database.
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24. Network DBs School of Information - The University of Texas at Austin
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25. Text-Oriented DBs
Text-oriented DBs are, as their name suggests, DBs that have special features for handling text: e.g., abilities
To search for specified strings of characters
With or without matching the cases of the characters
While using wildcards, i.e., symbols that will match any one character or any sequence of characters
To search on pairs, triples, etc., of words and phrases, using
Boolean logic
Proximity logic (e.g. both words must be in same sentence, or in same paragraph, or in same section, or within n words of each other)
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26. Text-Oriented DBs Abilities of text-oriented DBs, cont'd
To rank search results by weights assigned to the terms used in the search
To maintain thesauri of near synonyms and to allow searches by near synonyms of original query terms
To maintain, for selected words or phrases, indexes of their locations in files
Although commercial text-oriented DBs exist (e.g., Lexis-Nexis and Dialog), the only text-oriented DBMSs for microcomputers that I know of are askSam, DB/Textworks, and Isys. (From personal use, I can give askSam high marks for power and ease of use.)
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27. Geographic Information Systems
Geographic information systems (GISs) manage data based on geographic coordinates, usually obtained through the use of the Geographic Positioning System (GPS).
GISs typically integrate a variety of data relevant to such concerns as: atmosphere, ecology, environment, geology, natural resources, pollution, transportation, utilities, and characteristics and behaviors of populations (e.g., socioeconomic status, crimes, diseases, vehicular traffic).
The integrated data are displayed through the use of maps, which may include many overlapping, partly transparent layers.
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28. Advantages of RDBs Advantages of relational databases
Cut down on needless repetition of information
Ensure more accuracy
Facilitate updating and deletion of information.
Design avoids problems that occur with flat files, e.g., insertion and deletion anomalies
"Anomalies" are errors that occur when information is added to or deleted from existing records, or when whole records are added to or removed from a DB.
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29. Relational Databases
In a RDB, the information content of a table does not depend on either
The order of the rows; or
The order of the columns
In other words, the rows and columns of a table can be rearranged at will without affecting the table's information content
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30. Primary Keys In a RDB, each table A primary key is
Must have a primary key (unique identifier)
Must have no duplicate rows
A primary key is
A data attribute (column), or a combination of attributes, that uniquely identifies each record in the table.
A simple key consists of a single attribute
A composite key consists of two or more attributes
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31. Primary Keys Primary Key Provides unique way to identify each record
Can be obvious from the structure of the table. If there is no easy natural choice, you can add a column containing a unique identifier.
May consist of the entire record (especially with two-column tables, which occur often in the development of RDBs)
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32. Other Types of Keys Secondary Key Foreign Key
A column that is used to aid in the retrieval of information from a table. A secondary key is not required to have unique values in each of its rows,
Foreign Key
A column that is used to aid in the retrieval of information from one table (i.e., is a secondary key) and that is also the primary key in another table. Foreign keys are a major tool in RDBs.
All foreign keys are secondary keys, but not all secondary keys are foreign keys.
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33. Types of Fields Character Numeric Logical Image Object
LBO (Large Binary Object)
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34. Types of Fields
Character: Alphanumeric and punctuation. Character fields can include numerals, but calculations cannot be performed on the contents of the field even though they look like numbers.
Examples: Names, product codes, SSNs, ZIPCodes
Sometimes further differentiated between memo fields (short) and text fields (long)
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35. Types of Fields
Numeric: Arithmetic operations can be performed on the contents of the field
Numbers (sometimes further differentiated among integers [short, long], fixed-decimal point numbers, floating-point numbers)
Dates (addition and subtraction only)
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36. Types of Fields
General Rule for Numeric Fields: Never assign a field a numeric data type unless you intend to perform mathematical calculations on its contents.
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37. Types of Fields
Logical: True-False (T, F), Boolean (0, 1), Yes-No (Y, N)
Image: Used for relatively small graphics files (e.g., under 100KB)
Object: An object is a package of data together with program code that performs certain functions on the data
Large Binary Object: Used for very large items, such as multi-megabyte graphic, audio, and video files. The RDB typically merely stores pointers to the locations of these large files.
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38. What Is SQL? Structured Query Language (SQL)
Is pronounced either "S, Q, L" or "sequel"
Is a widely used standard set of commands and syntax for doing things with RDBMSs
Is used especially for query and retrieval
Includes commands for defining RDBs, conducting transactions, storing data, etc.
Is implemented in all major RDBMSs
SQL does not handle all the practical details involved in using a RDB, so every RDBMS has additional features unique to it
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39. History of SQL
A prototype DB query and retrieval language was developed by IBM in the early 1970s as "Sequel"
Other RDB developers and users recognized the advantage of a standard language for manipulating RDBs
This led to ANSI adoption of SQL as an enhanced RDB language based on Sequel
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40. Multiuser DBs
You are probably accustomed to using large Internet-based DBs as well as a DBMS on an individual microcomputer. In the latter case you are the only user of the DBMS and the DBs it handles, and you are also the manager of the DBMS.
In using a DBMS on an individual computer, you are unlike managers of multiuser DBMSs and DBs, in that you do not have to worry about questions of privacy and security—unless, of course, you are connected to the Internet or allow other people to use your computer.
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41. Multiuser DBs
You need to become aware that privacy and security are major concerns of multiuser DBMSs and DBs. With such DBMSs and DBs, much time and effort must be devoted to providing protection against violations of privacy and confidentiality, and against outright theft of data.
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42. Computerized Databases—
They can help to save you from this kind of work!
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43. References
Hernandez, Michael J. Database Design for Mere Mortals: A Hands-On Guide to Relational Database Design. Reading, MA: Addison-Wesley; p. ISBN: [A thorough, middle-level, readily understandable discussion of RDBs.]
Kawasaki, Guy. Database 101: A Database Primer for the Rest of Us. Berkeley, CA: Peachpit Press;  p. ISBN: [An exceptionally readable, elementary-level introduction to computerized databases. Unfortunately, it is now out-of-print, but some libraries may have a copy.]
Kroenke, David M. Database Processing: Fundamentals, Design and Implementation. Englewood Cliffs, NJ: Prentice-Hall; p. ISBN: [An advanced-level presentation of RDB theory and practice, but quite readable for that level.]
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44. References, cont'd
Meadow, Charles T.; Boyce, Bert R.; Kraft, Donald H. Text Information Retrieval Systems. 2nd ed. San Diego, CA: Academic Press; ISBN: [Without question, the authoritative source on text-oriented databases and text information retrieval.]
Monmonier, Mark. Spying with Maps: Surveillance Technologies and the Future of Privacy. Chicago, IL: University of Chicago Press; ISBN [An excellent introduction to geographic information systems, as well as to a variety of surveillance methods and their impacts on privacy.]
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45. References, cont'd
Taylor, Allen G. Database Development for Dummies. Foster City, CA: IDG Books Worldwide; ISBN: [Like other "for Dummies" books, this covers the basics well and is quite readable, though some may find its attempts at humor to be excessive.]
Taylor, Allen G. SQL for Dummies. Foster City, CA: IDG Books Worldwide; ISBN: [For comments, see the previous reference.]
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