tailieunhanh - Lecture Database concepts (3rd Edition): Chapter 2 - David M. Kroenke, David J. Auer

Chapter 2 - The relational model. In this chapter students will be able to: Learn the conceptual foundation of the relational model, understand how relations differ from nonrelational tables, learn basic relational terminology, learn the meaning and importance of keys, foreign keys, and related terminology, understand how foreign keys represent relationships. | The Relational Model Chapter Two DAVID M. KROENKE and DAVID J. AUER DATABASE CONCEPTS, 3rd Edition Chapter Objectives Learn the conceptual foundation of the relational model Understand how relations differ from nonrelational tables Learn basic relational terminology Learn the meaning and importance of keys, foreign keys, and related terminology Understand how foreign keys represent relationships 2- Chapter Objectives (continued) Learn the purpose and use of surrogate keys Learn the meaning of functional dependencies Learn to apply a process for normalizing relations 2- Entity An entity is something of importance to a user that needs to be represented in a database An entity represents one theme or topic In an entity-relationship model (discussed in Chapter 4), entities are restricted to things that can be represented by a single table 2- Relation A relation is a two-dimensional table that has specific characteristics The table dimensions, like a matrix, consist of rows and columns 2- Characteristics of a Relation Rows contain data about an entity Columns contain data about attributes of the entity Cells of the table hold a single value All entries in a column are of the same kind Each column has a unique name The order of the columns is unimportant The order of the rows is unimportant No two rows may be identical 2- A Sample Relation EmployeeNumber FirstName LastName 100 Mary Abernathy 101 Jerry Cadley 104 Alex Copley 107 Megan Jackson 2- A Nonrelation Example EmployeeNumber Phone LastName 100 335-6421, 454-9744 Abernathy 101 215-7789 Cadley 104 610-9850 Copley 107 299-9090 Jackson Cells of the table hold multiple values 2- EmployeeNumber Phone LastName 100 335-6421 Abernathy 101 215-7789 Cadley 104 610-9850 Copley 100 335-6421 Abernathy 107 299-9090 Jackson No two rows may be identical A Nonrelation Example 2- Terminology Table Row Column File Record Field Relation Tuple Attribute Synonyms 2- A Key A key is one (or more) . | The Relational Model Chapter Two DAVID M. KROENKE and DAVID J. AUER DATABASE CONCEPTS, 3rd Edition Chapter Objectives Learn the conceptual foundation of the relational model Understand how relations differ from nonrelational tables Learn basic relational terminology Learn the meaning and importance of keys, foreign keys, and related terminology Understand how foreign keys represent relationships 2- Chapter Objectives (continued) Learn the purpose and use of surrogate keys Learn the meaning of functional dependencies Learn to apply a process for normalizing relations 2- Entity An entity is something of importance to a user that needs to be represented in a database An entity represents one theme or topic In an entity-relationship model (discussed in Chapter 4), entities are restricted to things that can be represented by a single table 2- Relation A relation is a two-dimensional table that has specific characteristics The table dimensions, like a matrix, consist of rows and

• Cơ sở dữ liệu
• Database concepts
• Lecture Database concepts
• Database fundamentals
• Database design
• Database management
• Relational model
• Database system concepts
• Lecture Database system concepts
• Database systems
• Database languages
• Database system architectures
• Relational database design
• Database administration
• Database processing environment
• Relational databases
• Structured Query Language
• Data modeling
• Representing weak entities
• Query optimization
• Transaction state
• Concurrency control
• Recovery system
• Data analysis
• Information retrieval
• Parallel databases
• Distributed databases
• Advanced application development
• Advanced data types
• Advanced transaction processing
• Relational model
• Basic query structure
• Dynamic SQL
• Tuple relational calculus