1. MIS 301 Information Systems in Organizations Dave Salisbury salisbury@udayton.edusalisbury@udayton.edu (email) http://www.davesalisbury.com/http://www.davesalisbury.com/ (web site)

2. Things to know about Database Using Access QBE to Query Relational Databases (done) Querying Multi-table Databases (done) Using Logical Modeling to Create a Relational Database Translating a business situation into a data model, and then into a relational database

3. Databases & Data Modeling Data as a resource Samples of how databases are set up in organizations Basic logical modeling of data Basic physical modeling of data Data Integrity Normalization

4. Student ROI (Return on Investment) Your investment of time and effort in this course will result in your being able to answer these questions: How do knowledge workers use Access QBE to query a single-table database? How is Access QBE used to query multiple-table databases? How do knowledge workers use logical modeling to create effective relational database systems? How do you as a user participate in helping to build a database for your organization?

5. Disadvantages of File Processing Program-Data Dependence All programs maintain metadata for each file they use Data Redundancy (Duplication of data) Different systems/programs have separate copies of the same data Limited Data Sharing No centralized control of data Excessive Program Maintenance 80% of of information systems budget

6. Duplicate (Redundant) Data

7. Problems with Data Redundancy Waste of space to have duplicate data Causes more maintenance headaches The biggest Problem: When data changes in one file, could cause inconsistencies Compromises data integrity Lack of coordination and central control Non-standard file formats

8. Database Central repository of shared data Data is managed by a controlling agent Stored in a standardized, convenient form Requires a database management system (DBMS)

9. Advantages of Database Approach Program-Data Independence Metadata stored in DBMS, so applications don’t need to worry about data formats Minimal Data Redundancy Leads to increased data integrity/consistency Improved Data Sharing Different users get different views of the data Enforcement of Standards All data access is done in the same way Improved Data Quality Constraints, data validation rules

10. Modeling Reality A database must mirror the real world if it is to answer questions about the real world Data Modeling is a design technique for capturing reality STUDENT Social_Security_No Name Major

11. Using Logical Modeling to Create a Relational Database Most relational databases include many tables, not just one, to avoid redundancy. This redundancy can result in the database table taking up unneeded storage space as well as causing problems when trying to insert new records, delete existing records, or update records. These problems, typically referred to as anomalies, can harm the integrity of the database records. To create relational databases that avoid these problems with redundancy, logical modeling is used. The first step in logical modeling is to create an Entity- Relationship Diagram (ERD) that allow us to focus on the “big picture,” that is, the entities and the relationships.

12. Entity-Relationship Modeling One type of data modeling Entities – things you want to keep track of Relationships – how those things are related to one another

13. Notation in an ER diagram ENTITY RELATIONSHIP Something about which you want to keep data. How things you want to keep data about are tied together. = zero or = one or = many How to depict how many of one thing is related to how many of another.

14. Entity-Relationship Modeling Relationships imply constraints on how many entities may occur on one side (or the other) of a given relationship. Types of Relationships one-to-one 1:1 one-to-many 1:N many-to-many N:M

15. Entity-Relationship Diagramming The symbols for an ERD are (where 1:1 means a one- to-one relationship and 1:M means a one-to-many relationship):

16. Sample E-R Model Customer Order Product Places/ Placed by Contains/ is Contained in

17. Relational Databases Relations (a.k.a. tables) Each row is unique (entity instance) Order is unimportant Each column represents one thing (attribute) Entries are from the same domain (e.g. student)

18. Relational Databases Keys Primary key (uniquely identifies a record) Composite key, a.k.a. Concatenated key (two elements combined are unique) Foreign key (links tables/relations)

19. Data Integrity Rules to make sure your data is valid Entity integrity constraint Primary key cannot be null Referential integrity Ensures valid relationships between data Cannot add a row with no parent Cannot delete a parent without deleting child (cascading)

20. M:N Relationships in Relational Model Customer Order Order Line Places/ Placed by Contains/ is Contained in Product Contains/ is Contained in

21. How this looks in Access CustomerID FirstName LastName Address City State Zip Telephone OrderID OrderDate CustomerID OrderID ProductID Quantity ProductID Description Price Weight Supplier CUSTOMER ORDER ORDER LINE PRODUCT 1 8 1 8 1 8