XP Class Objectives – 9/10 and 9/12 Learn how to design a small database Understand the goals of a database Understand the terminology of database design Learn how to read a database design diagram Know how to create a database design diagram Implement a small custom database in MS Access Take a database design diagram and implement the resulting database in MS Access Create tables Create attributes with correct data types Create relationships and referential integrity constraints 1

XP Help available Your books!!!! Online help via Access and Excel Google (or other favorite search engine) Teaching Assistant (Robert Dittmer) Office hours: Monday andWednesday 10AM-noon Professor (Dana Edberg) Office hours: TR 1:15-2:15PM, 4-5PM 2

XP Questions for a systems developer What am I trying to accomplish by using a computer? Are you: Keeping track of lots of information for organization, customer, government, investor? Making processes more efficient requiring less labor? Facilitating decision making? Presenting information in a more readable, attractive format? What is the best way to accomplish your goals? Database management system? Spreadsheet? Web front end? Custom developed programs? Combination? 3

XP Book Example: Belmont Landscapes Company provides landscape architecture services including analyzing sites, developing plans and performing construction work. Wants to have a way to keep track of the work that will be done for customers (“contracts”) and then have a way to charge those customers (“invoices”) once the work has been completed. 4

Spreadsheet or Database for Belmont Landscapes? 5 Decision Issue Spreadsheet (Excel) Database (Access) Ability to maintain accurate data Limited. Completely dependent on user for accurate input. Excellent. Many filters/constraints available to protect data accuracy. Ease of showing data in different formats Limited. Can make small color changes to basic spreadsheet. Excellent. Very flexible. Data entered once can be viewed in many different formats. Ease of doing calculations Excellent. Statistics, financial functions available. Limited. Can do calculations, but only basic math. Difficulty of learning/using product Excellent. Easy to learn.Difficult to learn. Necessity for pre- planning Not much planning required. Must plan/design the database in advance.

XP Why do we store data in a database? To protect the “integrity” of the data. Make data accurate. Reduce data redundancy. To make data more accessible. Enhance flexibility of data access methods. Improve speed of data access. To make an application more adaptable. Provide more flexibility in application development. Decrease dependence on a given visualization method. 6

Examine the contract “spreadsheet” Review data content. What is the application? What is the purpose of the stored data? Is any of the data redundant? Why might redundant data be a problem? 7

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XP Vocabulary lesson - 1 Table: A two-dimensional database object used to store data. Row: One “entry” of data within the table. Must have a primary key that has a different value than all other rows of data within the table Column: A field used to store data. Must have a single data type. Cell: An intersection of a row and column. Can only have one data type and one value. 9

XP Vocabulary lesson - 2 Entity (when implemented it is called a “table”): A person, place, or thing about which we store data. Example is a Customer for Belmont Landscapes. Entity instance(also called a “record” or “row”): One instance of an entity that includes all data stored about that instance. Example is “Anthony Rodriquez” for Belmont. Attribute (also called a “field” or “column”): A characteristic of the entity about which we store data. Examples are Company, FirstName, Lastname for a Customer entity. 10

XP Process for Designing Databases Identify all the fields needed to produce the required information Divide each piece of data into its smallest useful part Example 1: Break up a name into first, last, initial Example 2: Break up an address into street, city, state, zip Group related fields into tables. Start with the “strong” tables. Use an entity-relationship diagram (ERD) to depict the design Determine each table’s primary key Identify how the tables are related (or if they are related) Include a common field in related tables (foreign key) Determine the properties of each field Type of data: Text, date, number, etc. Size of data Name of data 11

Contract Data 12

Group (sub-divide) the customer data 13

Group (sub-divide) the invoice data 14

XP What is a primary key? Definition Examples “Natural” vs. “Surrogate” 15

Define keys and relationships 16

What does it look like in Access? 17

XP What is a foreign key? Definition Example Depiction on diagrams 18

XP What is referential integrity? Definition: A constraint to enforce consistency between parent and child tables in a database. “Constraint”: A limit; a set of pre-defined rules. Conceptual example: Contract and customer. Implementation in Access example Create after a table has been created through the relationship diagram. Create while the table is being created through the use of a Lookup wizard. 19