1. Module 2 Designing a Logical Database Model

2. Module Overview Guidelines for Building a Logical Database Model Planning for OLTP Activity Evaluating Logical Models

3. Lesson 1: Guidelines for Building a Logical Database Model Guidelines for Transforming a Conceptual Database Design into a Logical Model Best Practices for Working with Entities and Attributes Considerations for Selecting Primary Keys Best Practices for Finalizing the Logical Model Discussion: Creating a Simple Database Model

4. Guidelines for Transforming a Conceptual Database Design into a Logical Model Use an automated design tool Design an initial ER diagram Use independent naming conventions Validate the ER diagram with the development team Use portable database types

5. Best Practices for Working with Entities and Attributes Identify independent and dependent entities Distinguish between tables and views Specify attribute constraints Identify special security requirements for attributes Identify candidate keys

6. Considerations for Selecting Primary Keys Natural keys have the following advantages: Enforced compliance Less joins Automatic constraints User verifiable Surrogate keys have the following advantages: Smaller size Better support for primary key changes Better availability Easier joins Surrogate Keys Natural Keys Each database table has a column or a combination of columns containing values that uniquely identify each row in the table

7. Best Practices for Finalizing the Logical Model Identify remaining constraints Identify schemas for grouping entities Normalize all data tables Compare the conceptual and logical models

8. Discussion: Creating a Simple Database Model Scenario: You are a database designer for a small school named Elm High School. The school management needs following data with respect to students and teachers: Tracking of each student The courses for which a particular student is enrolled and is/her grades for each term. Teachers who teach a particular course Students who learn from particular teachers In addition, the management needs the classroom allocation or scheduling information. Questions: Identify the probable entities and their characteristics. Discuss the differences and issues between the conceptual model and the logical model of the proposed database.

9. Lesson 2: Planning for OLTP Activity Guidelines for Identifying Functional Dependencies Benefits of Performing Data Normalization Degrees of Normalization Achieving a Normalized Design Guidelines for Performing Denormalization Discussion: Normalizing to an Absurd Level

10. Guidelines for Identifying Functional Dependencies Identify the semantics of attributes Identify the concepts of a relational schema Schema Relation Tuple Key Attribute

11. Benefits of Performing Data Normalization Reduce redundant values in tuples Reduce or eliminate null values in tuples Avoid generating spurious tuples

12. Degrees of Normalization First normal form (1NF) Relations do not contain any repeating groups Every attribute is atomic Relations do not contain any repeating groups Every attribute is atomic Third normal form (3NF) Relation is in the second normal form Some attributes of the relation are not transitively dependent on the primary key Relation is in the second normal form Some attributes of the relation are not transitively dependent on the primary key Name Age ID Second normal form (2NF) Relation is in the first normal form Attributes of the relation depend on the whole key Relation is in the first normal form Attributes of the relation depend on the whole key Name Age Skills Name E-mail Phone

13. Achieving a Normalized Design Ensure dependency of all values on simple and on composite keys Ensure that the design process is reversible Avoid update anomalies with normalization Ensure a high degree of normalization

14. Use denormalization when: Pre-aggregating data from other tables Avoiding multiple or complex joins Improving performance Pre-aggregating data from other tables Avoiding multiple or complex joins Improving performance Guidelines for Performing Denormalization Conditions to Denormalize a Design Performance with the normalized design is unacceptable Performance improves if denormalization is applied Update anomalies caused by denormalization can be predicted Performance with the normalized design is unacceptable Performance improves if denormalization is applied Update anomalies caused by denormalization can be predicted Simplifying data access Providing reporting data Preventing calculations based on values from the same row Simplifying data access Providing reporting data Preventing calculations based on values from the same row Avoid denormalization when:

15. Discussion: Normalizing to an Absurd Level Scenario: Normalization is about reducing duplicated data. 1234 Flower Blvd Normalize into the following fields: AddressNumber | AddressNameID | AddressTypeID 1234 412 14 AddressNameID 412 is ‘Flower’ in the AddressName table AddresssTypeID is ‘Blvd’ in the AddressType table Questions: Why would you not normalize to the level of absurdity? Provide a business scenario where an absurd level of data normalization could prove useful.

16. Guidelines for Analyzing an Existing Logical Model Identifying Problems with a Logical Model Discussion: Expanding Legacy Projects Lesson 3: Evaluating Logical Models

17. Guidelines for Analyzing an Existing Logical Model Validate the Accuracy of Documentation Validate the accuracy of documentation for an existing logical model Reverse Engineer the Model Reverse engineer the logical model if it differs significantly from the documented model

18. Identifying Problems with a Logical Model Analyze the model for consistency Identify anomalies that are caused by insufficient normalization Existing Logical Model

19. Discussion: Expanding Legacy Projects Scenario: Your development lead wants to add a new functionality to an existing data project. You cannot find any documentation about the design of the project. You cannot locate any change logs, bug logs or bug fixes. You have access to the current users and to the current production database. Question: How would you gather the required information to add a new functionality to the existing data project?

20. Lab 2: Designing a Logical Database Model Exercise 1: Creating a Logical Database Model Exercise 2: Normalizing the Logical Database Model Logon Information Estimated time: 60 minutes Virtual machine User name Password NYC-SQL1 Administrator Pa$$w0rd

21. Lab Scenario You are a lead database designer at QuantamCorp. You are working on the Human Resources Vacation and Sick Leave Enhancement (HR VASE) project, which is designed to enhance the current HR system of your organization. This system is based on the QuantamCorp2008 sample database in SQL Server 2008. The main goals of the HR VASE project are as follows: Provide managers with current and historical information about employee vacation and sick-leave data. Provide permission to individual employees to view their vacation and sick-leave balances. Provide permission to selected employees in the HR department to view and update employee vacation and sick-leave data. Provide permission to the HR manager to view and update all the data. Standardize employee job titles. The management has provided you with a Requirements document. The Requirements document contains information about business requirements, cost benefits, availability and reliability for business needs, security features, and performance requirements. The Requirements document also contains statements about how the HR department wants to store information about employee vacation and sick-leave hours. In lab 1, you created a conceptual model based on the Requirements document provided by the management. In this lab, you will build a logical model based on the conceptual model created earlier, and normalize its entities.

22. Lab Review Why do we need an intermediate table between the entities to support many-to-many relationships? How can we determine the column that can be used as a primary key? What are the key considerations while selecting a candidate for normalization? Why do you use composite primary keys very often in normalized tables?

23. Module Review and Takeaways Review Questions Real-world Issues and Scenarios Additional Reading Material

24. Notes Page Over-flow Slide. Do Not Print Slide. See Notes pane.