Rob Gleasure R.Gleasure@ucc.ie www.robgleasure.com IS6125 Database Analysis and Design Lecture 11: Normalization of Data Tables Rob Gleasure R.Gleasure@ucc.ie www.robgleasure.com

IS6125 Today’s session Normalisation Functional dependencies First normal form Second normal form Third normal form

Themes from the reports Three Vs Datafication and the Internet of Things Recording things is the first step Information asymmetry It’s bad for a market when one side knows more than the other about the quality of specific instances Privacy Data has value to a consumer Different types of data Self-reported data Trace/exhaust data Profiling data

Normalisation Not actually as terrifying as it sounds… Just about making a database as efficient as possible by breaking big tables with redundant data into smaller tables with less redundant data We do this by taking advantage of functional dependencies

Inferring Functional Dependencies (The Armstrong Axioms) 1. Reflexivity: If Y is a subset of X, then X Y 2. Augmentation: If X Y, then XZ YZ 3: Transitivity: If X Y, and Y Z, then X Z

Normalisation: Orders Table Full_ Name Address Zone Order _ID Date Product_1 Cost_P1 Units_P1 Product_2 Cost_P2 Units_P2 Product_3 Cost_P3 Units_ P3 John Murphy 123 Fake St Inner-city S345 31/12/ 2014 Football $20.00 2 Gloves $53.50 1 Whistle $5.00 Mary Byrne Kildaman-fadar Rural R367 9/9/ Helmet $30.50 Anne Dunne N654 10/6/ Pants $13.75 Hat $11.00 Jim Feltz 20c Fake St D896 13/06/ $28.75 Boots $75.95 S354 1/01/ 2015 Socks $3.50 5

Normalisation: First Normal Form Name Address Zone Order _ID Date Product Cost Units John Murphy 123 Fake St Inner-city S345 31/12/ 2014 Football $20.00 2 Gloves $53.50 1 Whistle $5.00 S354 Socks $3.50 5 Mary Ahern Kildaman-fadar Rural R367 9/9/ Helmet $30.50 Anne Dunne N654 10/6/ Pants $13.75 Hat $11.00 Jim Feltz 20c Fake St D896 13/06/ $28.75 Boots $75.95

First Normal Form (continued) Name Last_ Address Zone Order _ID Date Product Cost Units John Murphy 123 Fake St Inner-city S345 31/12/ 2014 Football $20.00 2 Gloves $53.50 1 Whistle $5.00 S354 Socks $3.50 5 Mary Byrne Kildaman-fadar Rural R367 9/9/ Helmet $30.50 Anne Dunne N654 10/6/ Pants $13.75 Hat $11.00 Jim Feltz 20c Fake St D896 13/06/ $28.75 Boots $75.95

Summary of First Normal Form (1NF) A database is in the first normal form when Attributes store only atomic values Duplicate columns are removed

Moving to Second Normal Form First_ Name Last_ Address Zone Order _ID Date Product Cost Units John Murphy 123 Fake St Inner-city S345 31/12/ 2014 Football $20.00 2 Gloves $53.50 1 Whistle $5.00 S354 Socks $3.50 5 Mary Byrne Kildaman-fadar Rural R367 9/9/ Helmet $30.50 Anne Dunne N654 10/6/ Pants $13.75 Hat $11.00 Jim Feltz 20c Fake St D896 13/06/ $28.75 Boots $75.95

Second Normal Form Cust_ID Order _ID Date Product Cost Units Cust_ID 1 S345 31/12/ 2014 Football $20.00 2 Gloves $53.50 Whistle $5.00 S354 Socks $3.50 5 R367 9/9/ Helmet $30.50 3 N654 10/6/ Pants $13.75 Hat $11.00 4 D896 13/06/ $28.75 Boots $75.95 Cust_ID First_ Name Last_ Address Zone 1 John Murphy 123 Fake St Inner-city 2 Mary Byrne Kildaman-fadar Rural 3 Anne Dunne 4 Jim Feltz 20c Fake St

Second Normal Form (Continued) Cust_ ID Order _ID Date Product Units 1 S345 31/12/ 2014 2 3 S354 4 5 R367 9/9/ N654 10/6/ 6 7 D896 13/06/ 8 Cust_ ID First_ Name Last_ Address Zone 1 John Murphy 123 Fake St Inner-city 2 Mary Byrne Kildaman-fadar Rural 3 Anne Dunne 4 Jim Feltz 20c Fake St Product_ID Product_1 Cost_P1 1 Football $20.00 2 Gloves $53.50 3 Whistle $5.00 4 Socks $3.50 5 Helmet $30.50 6 Pants $13.75 7 Hat $11.00 8 Boots $75.95

Second Normal Form (Continued) Cust_ID Order _ID Product Units 1 S345 2 3 S354 4 5 R367 N654 6 7 D896 8 Cust_ ID First_ Name Last_ Address Zone 1 John Murphy 123 Fake St Inner-city 2 Mary Byrne Kildaman-fadar Rural 3 Anne Dunne 4 Jim Feltz 20c Fake St Order _ID Date S345 31/12/ 2014 S354 R367 09/09/ N654 10/6/ D896 13/06/ Product_ID Product_1 Cost_P1 1 Football $20.00 2 Gloves $53.50 3 Whistle $5.00 4 Socks $3.50 5 Helmet $30.50 6 Pants $13.75 7 Hat $11.00 8 Boots $75.95

Second Normal Form (Continued) Order _ID Product Units S345 1 2 3 S354 4 5 R367 N654 6 7 D896 8 Cust_ ID First_ Name Last_ Address Zone 1 John Murphy 123 Fake St Inner-city 2 Mary Byrne Kildaman-fadar Rural 3 Anne Dunne 4 Jim Feltz 20c Fake St Order _ID Cust_ ID S345 1 R367 2 N654 3 D896 4 Order _ID Date S345 31/12/ 2014 S354 R367 09/09/ N654 10/6/ D896 13/06/ Product_ID Product_1 Cost_P1 1 Football $20.00 2 Gloves $53.50 3 Whistle $5.00 4 Socks $3.50 5 Helmet $30.50 6 Pants $13.75 7 Hat $11.00 8 Boots $75.95

Summary of Second Normal Form (2NF) A database is in the second normal form when It satisfies the criteria for the first normal form Each non-candidate key is dependent on the whole candidate key (i.e. subsets of data across multiple rows are removed) Put differently, we have no partial dependencies via a concatenated key Takes advantage of reflexivity and augmentation

Moving to Third Normal Form Order _ID Product Units S345 1 2 3 S354 4 5 R367 N654 6 7 D896 8 Cust_ ID First_ Name Last_ Address Zone 1 John Murphy 123 Fake St Inner-city 2 Mary Byrne Kildaman-fadar Rural 3 Anne Dunne 4 Jim Feltz 20c Fake St Order _ID Cust_ ID S345 1 R367 2 N654 3 D896 4 Order _ID Date S345 31/12/ 2014 S354 R367 09/09/ N654 10/6/ D896 13/06/ Product_ID Product_1 Cost_P1 1 Football $20.00 2 Gloves $53.50 3 Whistle $5.00 4 Socks $3.50 5 Helmet $30.50 6 Pants $13.75 7 Hat $11.00 8 Boots $75.95

Moving to Third Normal Form Order _ID Product Units S345 1 2 3 S354 4 5 R367 N654 6 7 D896 8 Cust_ ID First_ Name Last_ Address 1 John Murphy 123 Fake St 2 Mary Byrne Kildaman-fadar 3 Anne Dunne 4 Jim Feltz 20c Fake St Order _ID Cust_ ID S345 1 R367 2 N654 3 D896 4 Order _ID Date S345 31/12/ 2014 S354 R367 09/09/ N654 10/6/ D896 13/06/ Address Zone 123 Fake St Inner-city 20c Fake St Kildaman-fadar Rural Product_ID Product_1 Cost_P1 1 Football $20.00 2 Gloves $53.50 3 Whistle $5.00 4 Socks $3.50 5 Helmet $30.50 6 Pants $13.75 7 Hat $11.00 8 Boots $75.95

Summary of Third Normal Form (3NF) A database is in the second normal form when It satisfies the criteria for the second normal form Each non-key attribute that depends on anything other than the entire primary key is removed (insertion anomalies are impossible) Put differently, we have no transitive dependencies via non-key attributes Takes advantage of transitivity

Readings Some more descriptions of normal forms http://databases.about.com/od/specificproducts/a/normalization.htm http://phlonx.com/resources/nf3/ http://www.bkent.net/Doc/simple5.htm