Understanding Relational Database Concepts Professor Larry Heimann Carnegie Mellon University Lecture Notes — Fall 1999

Today’s Hidden Agenda Announcements and such Why Relational Databases Types of Relations Keys and Key Rings Integrity in Relational Databases Types of Data

Now Opening: Now Opening: Monadnock Book Store What functions does the Monadnock Book Store need to be a successful venture? Advantages to using a computer for record keeping

What Type of Database for MBS? Flat file database is easy to understand and set-up -- even for the computer novices. What would a flat file database look like for MBS? What are some of the problems with using a flat-file database for MBS operations?

A Possible Flat File Database for MBS

An Alternative: Relational Databases Relational databases consist of a series of data tables linked together so that data can later be combined and extracted as needed. Some terminology –table / file –column / field –row / record AutIDAutFirstNameAutLastName 0150LarryHeimann 0151CharlesHummel 0152MichaelBehe 0153MarcOrkand tblAuthor

Codd’s Rule…Condensed Version represent all information in the database as tables keep the logical representation of data independent from its physical storage characteristics use SQL for structuring, querying, and changing information in the database support the main relational operations (selection, projection, join) and set up operations such as union, intersection, difference, and division support views, which allow the user to specify alternative ways of looking at data in tables provide a method for differentiating between unknown values (nulls) and zero or blank support mechanisms for integrity, authorization, transactions, and recovery

A Glimpse at the MBS RDB AutID AutFirstName AutLastName AutBioSketch AutInterview AutID ISBN EditionNumber CopyrightYear ISBN PubID RetailPrice Rating CoverPicture PubID PubName PubAddress PubCity PubState PubZIP PubPhone PubFax SalesID ISBN SalesQuantity SalesID SalesDate CustID ShipDate CustID CustFirstName CustLastName CustAddress CustCity CustState CustZIP CustPhone Cust CreditCardType CreditCardNum CardExp tblCustomer tblBook tblSaleDetail tblBookAuthor tblAuthor tblPublisher tblSales 1 ∞ ∞ 1 1 ∞ 1 ∞ ∞ ∞ 1 1

Relations in the MBS Database One-to-One Relations One-to-Many Relations Many-to-Many Relations These relationships are represented different ways depending on the type of model being used.

Keys in a Relational Database How can we be sure we are accessing the correct records? Primary Keys Composite Keys Foreign Keys

Integrity -- Important in People and in Databases 1st Type: Entity Integrity 2nd Type: Domain Integrity 3rd Type: Referential Integrity

Potential Problem Areas Bad input data Operator error Mechanical failure Malice Data Redundancy

What Kind of Data Can We Store? Exact numerics Approximate numerics character strings bit strings datetimes intervals