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Chapter 7 Database Design

Chapter 7 Database Design. UML Specification for Data Modeling The Relational Data Model and Object Model Persistence Frameworks Database Design. UML Specification for Data Modeling. 7.1 UML Specification for Data Modeling. UML Notation for Data Modeling

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Chapter 7 Database Design

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  1. Chapter 7 Database Design • UML Specification for Data Modeling • The Relational Data Model and Object Model • Persistence Frameworks • Database Design

  2. UML Specification for Data Modeling

  3. 7.1 UML Specification for Data Modeling • UML Notation for Data Modeling • Modeling Associations in the Data Model • Modeling Aggregation in the Data Model • Modeling Inheritance in the Data Model

  4. UML Notation for Data Modeling

  5. CourseOffering - number : String 0..* 0..* Course - name 1 - description - number Modeling Associations in the Data Model • Associations between two persistent objects are realized as foreign keys to the associated objects. • A foreign key is a column in one table which contains the primary key value of associated object Course Offering table Foreign Key Primary Key Course table

  6. Modeling Aggregation in the Data Model • Aggregation is also modeled using foreign key relationships • Using composition implements a cascading delete constraint Student table Student. - studentID : int Primary Key 1 1 0..* 0..* Foreign Key Schedule table Schedule - semester : Semester

  7. Modeling Inheritance in the Data Model • A data model does not support modeling inheritance in a direct way • Two options • Use separate tables (normalized data) • Duplicate all inherited associations and attributes (de-normalized data)

  8. Modeling Inheritance in the Data Model - Example

  9. Modeling Inheritance in the Data Model - Example

  10. Modeling Inheritance in the Data Model - Example

  11. Modeling Inheritance in the Data Model - Example

  12. Modeling Inheritance in the Data Model - Example

  13. The Relational Data Model and Object Model

  14. 7.2 The Relational Data Model and Object Model • The Relational Data Model • The Object Model

  15. The Relational Data Model • The relational model is composed of entities and relations. An entity may be a physical table or a logical projection of several tables also known as a view.

  16. The Object Model • An object model contains classes. Classes define the structure and behavior of a set of objects, sometimes called objects instances. The structure is represented as attributes (data values) and associations (relationships between classes).

  17. The Persistence Frameworks

  18. 7.3 Persistence Frameworks • The Purpose of a Persistence Framework • Hibernate

  19. The Purpose of a Persistence Framework

  20. Hibernate • Object / Relational mapping (ORM) and persistence / query framework • i.e. It does even more stuff for you! • Some features of Hibernate • HibernateDaoSupport – superclass, easy HibernateTemplate access • Database independence - sits between the database and your java code, easy database switch without changing any code • Object / Relational Mapping (ORM) - Allows a developer to treat a database like a collection of Java objects • Object oriented query language (HQL) - *Portable* query language, supports polymorphic queries etc. • You can also still issue native SQL, and also queries by “Criteria” (specified using “parse tree” of Java objects) • Hibernate Mapping - Uses HBM XML files to map value objects (POJOs) to database tables • Transparent persistence - Allows easy saves/delete/retrieve for simple value objects • Very high performance “in general” due to intelligent (2-level) caching, although in a few cases hand-written SQL might beat it

  21. Hibernate • Hibernate basically sits between the DB and your code • Can map persistent objects to tables

  22. Database Design

  23. 7.4 Database Design • Purpose • Overview • Steps • Map persistent design classes to tables • Distribute class behavior to the database

  24. Purpose • To ensure that persistent data is stored consistently and efficiently. • To define behavior that must be implemented in the database.

  25. Supplementary Specifications DesignGuidelines Data Model Design Classes Database Design Overview Use-Case Realization Database Design

  26. Steps • Map Persistent Design Classes to the Data Model • Optimize the Data Model for Performance • Optimize Data Access • Define Storage Characteristics • Define Reference Tables • Define Data and Referential Integrity Enforcement Rules • Distribute Class Behavior to the Database • Review the Results

  27. Mapping Persistent Classes to Tables • In a relational database • Every row is regarded as an object • A column in a table is equivalent to a persistent attribute of a class Attributes from object type Object Instance

  28. Mapping Persistent Classes to Tables - Example

  29. Map Class Behavior to Stored Procedures • Determine if any operations can be implemented as a stored procedure • Candidate operations • Deal with persistent data • Any operations where a query is involved in a computation • Need to access the database to validate data

  30. What Are Stored Procedures? • A stored procedure is executable code which runs under the RDBMS • Two types of stored procedures • Procedures: Executed explicitly by an application • Triggers: Invoked implicitly when some database event occurs

  31. Example: Map Class Behavior to Stored Procedures Class Candidate Operations • getTuition • addSchedule • getSchedule • deleteSchedule • getStudentID • getName • getAddress

  32. Example: Map Class Behavior to Stored Procedures

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