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Database design & Normalization (1NF, 2NF, 3NF)

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Brief introduction about database design & Database normalization basics

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Database design & Normalization (1NF, 2NF, 3NF)

  1. 1. www.lib.ku.edu/instruction Database Design Practical Database Design for Relational Database Management Systems Overview A little background and terminology: What is a relational database? What is a primary key? What is a foreign key? Things to know about designing a database: The normalization process and how/why use it Relating tables Types of relationships 9/19/07 2© 2007 Instructional Services at KU Libraries, The University of Kansas
  2. 2. www.lib.ku.edu/instruction Relational Database Management System Collection of information organized in tables Tables are also “relations” Tables are constructed and associated to each other through shared fields–“common” fields Fields are also “columns” or “attributes” A set of attributes comprises a record Records are also “rows” or “tuples” Tables are related through common fields designated as primary and foreign keys Allow us to find, update, and delete data quickly, and help to ensure accuracy 9/19/07 3 Primary and Foreign Key Fields Primary Key Primary key fields must be unique and cannot contain a null value. Each table should have a primary key field. Concatenated keys: using more than one field as a primary key field. Foreign Key: Fields in a table that refer to the primary key in another table The data in this field must exactly match data contained in the primary key field. 9/19/07 4© 2007 Instructional Services at KU Libraries, The University of Kansas
  3. 3. www.lib.ku.edu/instruction What is Normalization? The process by which we efficiently organize data to achieve these goals: Eliminating redundancy Ensuring data is stored in the correct table Eliminating need for restructuring database when data is added. Five levels of normal form In order to achieve one level of normal form, each previous level must be met Third normal form is sufficient for most typical database applications. 9/19/07 5 First Normal Form (1NF) There are no repeating or duplicate fields. Each cell contains only a single value. Each record is unique. Identified by primary key 9/19/07 6© 2007 Instructional Services at KU Libraries, The University of Kansas
  4. 4. www.lib.ku.edu/instruction Example item colors price tax T-shirt red, blue 12.00 0.60 polo red, yellow 12.00 0.60 T-shirt red, blue 12.00 0.60 sweatshirt blue, black 25.00 1.25 Table is not in first normal form because: Multiple items in color field Duplicate records / no primary key 9/19/07 7 Example item color price tax T-shirt red 12.00 0.60 T-shirt blue 12.00 0.60 polo red 12.00 0.60 polo yellow 12.00 0.60 sweatshirt blue 25.00 1.25 sweatshirt black 25.00 1.25 Table is now in first normal form. 9/19/07 8© 2007 Instructional Services at KU Libraries, The University of Kansas
  5. 5. www.lib.ku.edu/instruction Second Normal Form (2NF) All non-key fields depend on all components of the primary key. Guaranteed when primary key is a single field. 9/19/07 9 Example item color price tax T-shirt red 12.00 0.60 T-shirt blue 12.00 0.60 polo red 12.00 0.60 polo yellow 12.00 0.60 sweatshirt blue 25.00 1.25 sweatshirt black 25.00 1.25 Table is not in second normal form because: price and tax depend on item, but not color 9/19/07 10© 2007 Instructional Services at KU Libraries, The University of Kansas
  6. 6. www.lib.ku.edu/instruction Example item color item price tax T-shirt red T-shirt 12.00 0.60 T-shirt blue polo 12.00 0.60 polo red sweatshirt 25.00 1.25 polo yellow sweatshirt blue sweatshirt black Tables are now in second normal form. 9/19/07 11 Third Normal Form (3NF) No non-key field depends upon another. All non-key fields depend only on the primary key. 9/19/07 12© 2007 Instructional Services at KU Libraries, The University of Kansas
  7. 7. www.lib.ku.edu/instruction Example item color item price tax T-shirt red T-shirt 12.00 0.60 T-shirt blue polo 12.00 0.60 polo red sweatshirt 25.00 1.25 polo yellow sweatshirt blue sweatshirt black Tables are not in third normal form because: tax depends on price, not item 9/19/07 13 Example item color item price T-shirt red T-shirt 12.00 T-shirt blue polo 12.00 polo red sweatshirt 25.00 polo yellow sweatshirt blue price tax sweatshirt black 12.00 0.60 25.00 1.25 Tables are now in third normal form. 9/19/07 14© 2007 Instructional Services at KU Libraries, The University of Kansas
  8. 8. www.lib.ku.edu/instruction Another Example Name Assignment 1 Assignment 2 Jeff Smith Article Summary Poetry Analysis Nancy Jones Article Summary Reaction Paper Jane Scott Article Summary Poetry Analysis Table is not in first normal form because: Assignment field repeating First and last name in one field No (guaranteed unique) primary key field 9/19/07 15 Another Example Assignment ID Description 1 Article Summary Assignment ID Student ID 2 Poetry Analysis 1 1 3 Reaction Paper 1 2 1 3 2 1 Student ID First Name Last Name 2 3 1 Jeff Smith 3 2 2 Nancy Jones 3 Jane Scott Tables are in third normal form. 9/19/07 16© 2007 Instructional Services at KU Libraries, The University of Kansas
  9. 9. www.lib.ku.edu/instruction Relationships Relationships are created between tables using the primary key field and a foreign key field One to One Relationship One record in a table relates to one record in another table One to Many Relationship One record in a table can relate to many records in another table Many to Many Relationship Many records in one table can relate to many records in another table 9/19/07 17 Relationships in First Example item color item price T-shirt red T-shirt 12.00 T-shirt blue polo 12.00 polo red sweatshirt 25.00 polo yellow sweatshirt blue sweatshirt black price tax one to one 12.00 0.60 one to many 25.00 1.25 9/19/07 18© 2007 Instructional Services at KU Libraries, The University of Kansas
  10. 10. www.lib.ku.edu/instruction Relationships in Second Example Assignment ID Description 1 Article Summary Assignment ID Student ID 2 Poetry Analysis 1 1 3 Reaction Paper 1 2 1 3 2 1 2 3 Student ID First Name Last Name 3 2 1 Jeff Smith one to one 2 Nancy Jones one to many 3 Jane Scott many to many 9/19/07 19 Bibliography Hernandez, Michael J. Database Design for Mere Mortals. San Francisco: Addison-Wesley, 1997. Chapple, Mike. “ Database Normalization Basics.” 5 August 2001. Online. Internet. Available http://databases.about.com/library/weekly/aa080501a.htm Association for Geographic Information. GIS Dictionary. 1999. Online. Internet. Available http://www.geo.ed.ac.uk/agidexe/term?821 Wise, Barry. “Database Normalization and Design Techniques.” 1 August 2000. 6 pp. Online. Internet. Available http://www.phpbuilder.com/columns/barry20000731.php3 9/19/07 20© 2007 Instructional Services at KU Libraries, The University of Kansas
  11. 11. www.lib.ku.edu/instruction Further Reading Harrington, Jan L. Relational Database Design Clearly Explained. San Diego: Academic Express, 1998. Chapple, Mike. “Choosing a Database Product.” 6 May 2001. Online. Internet. Available http://databases.about.com/library/weekly/aa050601a.htm Gilmore, W.J. “Introduction to Database Normalization.” 27 November 2000. Online. Internet. Available http://www.devshed.com/Server_Side/MySQL/Normal/Normal 1/page1.html 9/19/07 21© 2007 Instructional Services at KU Libraries, The University of Kansas

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