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Unformatted text preview: ntered until a P.O. new number is issued number • Therefore, a new vendor could not be entered until Therefore, the first purchase occurred the Delete Anomaly Delete Unintended results when deleting a row in a Unintended table that contains all data table Example: only one item has been purchased Example: from a vendor from
• Deleting that row would delete all information Deleting about the vendor about Un-normalized Data Un-normalized
Registrar’s view of university student enrollment (unnormalized database):
Stu Num Stu Name 6432 Adams Major ACCT Course ACCT2331 ACCT2332 MATH1421 7689 8653 Shinn Miller MANA ACCT MANA2366 HIST1010 ACCT4397 MATH1421 MANA2366 Crse Name Fin Acct Mgt Acct Calculus Intro Mgt US Hist Ind Study Calculus Intro Mgt Professor Stinson Francia Smith Phillips Archer Stinson Smith Phillips Office 390 370 230 343 285 390 230 343 Phone Grade 34898 34825 31892 32788 33561 34898 31892 32788 A B B C B B B C What are examples of What •Delete anomaly? •Update anomaly? •Insert anomaly? Normalization Normalization
Normalization is one approach to designing well-structured databases to (more later) Potential Impact of Database Systems on Traditional Accounting Traditional Elimination of double entry accounting redundancy • Trial balances are redundant checks • Computer can do it Changes in financial reporting & managerial decision making • Database available to users • Users determine their own needs Users • Integration of operating and financial data (Wal Mart) Types of Query Languages Types Text based: Structured Query Language (SQL) Graphical: used by Access This is all you are responsible for from the appendix
• We won’t use SQL (take the MIS database course) • We will use the graphical language of Access END OF CHAPTER 4 END MS Access Assignment Database Design Database NOT IN THE BOOK Learning Objectives Learning List the steps for database design List the steps in the normalizations process Understand the normalization process Database Design Database
Steps for Converting User Views to Underlying Tables Identify user views Create an unnormalized table for each user view Determine table relationships (1:1, 1:N, M:N) Identify foreign keys (and place in tables) Add database attributes Normalize the tables Database Design Database
Steps for Converting User Views to Underlying Tables Identify user views Create an unnormalized table for each user view Determine table relationships (1:1, 1:N, M:N) Identify foreign keys (and place in tables) Add database attributes the topic for today Normalize the tables Normalization Normalization Eliminates anomaly-causing dependencies: Repeating groups Partial dependencies Transitive dependencies Anomalies Anomalies Update anomaly
Cause: Insertion anomaly
Cause: Deletion anomaly
Cause: Normalization Normalization Splits unnormalized tables into smaller tables such Splits that that • • Tables that meet these are in third normal form (3NF) Look for “themes” for each table Boyce-Codd NF, 4NF, 5NF, and Domain Key NF are Boyce-Codd possible but usually not necessary (no practical application for 5NF) application The Normalizati...
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This note was uploaded on 10/02/2010 for the course ACCT 5457 taught by Professor Polm during the Fall '10 term at Rensselaer Polytechnic Institute.
- Fall '10