overview of database concept
- 1. Overview of Database Concepts
- 2. Chapter Objectives • Identify the purpose of a database management system (DBMS) • Distinguish a field from a record and a column from a row • Identify the basic components of an Entity- Relationship Model • Define the three types of relationships that can exist between entities
- 3. Chapter Objectives • Identify the problem associated with many- to-many relationships and the appropriate solutions • Explain the purpose of normalization • Describe the role of a primary key • Identify partial dependency and transitive dependency in the normalization process
- 4. Chapter Objectives • Explain the purpose of a foreign key • Determine how to link data in different tables through the use of a common field • Explain the purpose of a structured query language (SQL)
- 5. Database Terminology • Database – logical structure to store data • Database Management System (DBMS) – software used to create and interact with the database
- 6. Database Components • Character • Field • Record • File
- 7. Database Components - Character • Basic unit of data • Can be a letter, number, or special symbol
- 8. Database Components - Field • A group of related characters • Represents an attribute or characteristic of an entity • Corresponds to a column in the physical database
- 9. Database Components - Record • A collection of fields for one specific entity • Corresponds to a row in the physical database
- 10. Database Components - File • A group of records about the same type of entity
- 12. Review of Database Design • Systems Development Life Cycle (SDLC) • Entity-Relationship Model (E-R Model) • Normalization
- 13. Systems Development Life Cycle (SDLC) • Systems investigation – understanding the problem • Systems analysis – understanding the solution • Systems design – creating the logical and physical components
- 14. Systems Development Life Cycle (SDLC) • Systems implementation – placing completed system into operation • Systems maintenance and review – evaluating the implemented system
- 15. Entity-Relationship Model (E-R Model) • Used to depict the relationship that exists among entities
- 17. Relationships • The following relationships can be included in an E-R Model: – One-to-one – One-to-many – Many-to-many
- 18. One-to-one Relationship • Each occurrence of data in one entity is represented by only one occurrence of data in the other entity • Example: Each individual has just one Social Security Number (SSN) and each SSN is assigned to just one person
- 19. One-to-many Relationship • Each occurrence of data in one entity can be represented by many occurrences of the data in the other entity • Example: A class has only one instructor, but each instructor can teach many classes
- 20. Many-to-many Relationship • Data can have multiple occurrences in both entities • Example: A student can take many classes and each class is composed of many students
- 22. Normalization • Determines required tables and columns for each table • Multi-step process allows designer to take the raw data to be collected about an entity • Used to reduce or control data redundancy
- 23. Attributes of Books • isbn : a value string used to identify any book. • Title: Book’s title • Publication Date: A value of DATE type. • Cost: Publisher’ price • Retail: Sale’s price. • Category: Computer, Fiction Science, etc. • Publisher: Publisher’ house. • Contact: Sale representative.
- 25. Unnormalized Data Contains repeating groups in the Author column in the BOOKS table
- 26. First-Normal Form (1NF) • Primary key is identified. A Primary key is a field that serves to uniquely identify each record. • Repeating groups are eliminated (each entry a separated record).
- 27. First-Normal Form (1NF) ISBN and Author columns together create a composite primary key
- 28. Composite Primary Key • More than one column is required to uniquely identify a row • When a primary key consists of more or one field, another problem may occurs--- partial dependency - a column/ns is/are only dependent on a portion of the primary key The fields describing the book depend of the book itself not upon who wrote.
- 29. Second-Normal Form (2NF) • Partial dependency must be eliminated – Break the composite primary key into two parts, each part representing a separate table (for example, Author)
- 30. Second-Normal Form (2NF) BOOKS table in 2NF
- 31. Third-Normal Form (3NF) Publisher contact name has been removed
- 32. Summary of Normalization Steps • 1NF: eliminate repeating groups, identify primary key • 2NF: table is in 1NF and partial dependencies eliminated • 3NF: table is in 2NF and transitive dependencies eliminated
- 33. Linking Tables • Once tables are normalized, make certain tables are linked • Tables are linked through a common field • A common field is usually a primary key in one table and a foreign key in the other table
- 35. Graphical Representation for Books Column Name ISBN Title Publication Date Cost Retail Category PublId Key Type PK FK1 Null/ Unique NN,U NN FK Ref Table Publisher FK Ref Columns PublId Data type CHAR CHAR DATE NUMBER NUMBER CHAR NUMBER Maximum Length 10 35 11 11 25 5 Sample Data 8843172113 DATABASE 11/AGO/2003 69.75 89.75 computers 1234
- 36. Lab # 1 • Find the graphical representations of tables considered in the Pet Shop.
- 37. Specialization • Top-down design process; we designate subgroupings within an entity set that are distinctive from other entities in the set. • These subgroupings become lower-level entity sets that have attributes or participate in relationships that do not apply to the higher-level entity set. • Depicted by a triangle component labeled ISA (E.g. customer “is a” person). • Attribute inheritance – a lower-level entity set inherits all the attributes and relationship participation of the higher-level entity set to which it is linked.
- 38. Generalization • A bottom-up design process – combine a number of entity sets that share the same features into a higher-level entity set. • Specialization and generalization are simple inversions of each other; they are represented in an E-R diagram in the same way. • The terms specialization and generalization are used interchangeably.
- 39. UML • UML: Unified Modeling Language • UML has many components to graphically model different aspects of an entire software system • UML Class Diagrams correspond to E-R Diagram, but several differences.
- 40. Structured Query Language (SQL) • Data sublanguage • Used to: – Create or modify tables – Add data to tables – Edit data in tables – Retrieve data from tables