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Database Organization and Design. Chapter 1 Adapted from slides by Raghu Ramakrishnan, What is a DBMS?. A database is a (very) large, integrated collection of data A database is based upon a data representation (data model) of a real-world enterprise

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database organization and design

Database Organization and Design

Chapter 1

Adapted from slides by Raghu Ramakrishnan,

what is a dbms
What is a DBMS?
  • A database is a (very) large, integrated collection of data
  • A database is based upon a data representation (data model) of a real-world enterprise
    • Objects (or Entities, e.g., students, courses)
    • Relationships (e.g., Charlie Brown is in CS3610)
  • A Database Management System (DBMS) is a software package designed to store and manage databases. E.g., UNIDATA, mysql, or Access
file storage vs a dbms
File Storage vs. a DBMS
  • A DBMS can “stage” data (for large datasets) between main memory and secondary sources (disk, CD, tape)
  • A DBMS provides efficient (indexed) access
  • A DBMS provides a built-in query language to facilitate data retrieval
    • Permits free form queries
    • Standard language provides standard communication for programs using embedded queries
  • A DBMS protects data from inconsistency by
    • Enforcing referential integrity during data modification
    • Enforcing data format constraints
    • Providing controlled concurrent access
  • A DBMS provides crash recovery
  • A DBMS provide multi-level security and access control
  • A DBMS allows for uniform administration of the data
data models
Data Models
  • A data model is the manner in which you describe some data.
    • The Entity Relationship Diagram (ERD) represents a conceptual data model for describing objects and their relationships. The ERD is the most common of the conceptual data models. It has several variants.
      • Main features of an ERD is entities, attributes, and relationships.
    • The relational data model is a conceptual data model for implementing a database. The relational model is easily the most widely used model today.
      • Main concept the relation: a table of records and fields
      • Every relation has a defining schema
  • A schema is the description of a particular collection of data in a given data model.
levels of abstraction
Levels of Abstraction

View 1

View 2

View 3

Conceptual Schema

Physical Schema

example university database
Example: University Database
  • External View:
    • View1: course_info ( course_name, enrollment )
    • View2: teacher_info ( course_name, teacher )
  • Conceptual Schema
    • Students(sid, name, age, gpa)
    • Courses (cid, name, credits)
    • Teachers (tid, name, rank)
    • Enrolled (sid, cid, grade)
    • Teaches (tid, cid)
  • Physical Schema
    • Store relations as tables
    • Index tables by id fields
road ahead
Road Ahead
  • Modeling Data with Entity Relationship Diagrams
  • Using the Relational Model (i.e., Schema Descriptions) to Model Data
  • Relational Algebra: A concise language for describing data operations
  • Structured Query Language (SQL): A standard language for manipulation of data by computers
  • Database Apps: Learning how to access databases from programs
  • Database File Organization, Storage, and Indexing
road ahead continued
Road Ahead (Continued)
  • Hash Indexes
  • Query Evaluation: Getting the resultant data for the (somewhat) least cost
  • Transaction Management: Keeping multiple users from interfering with each other
  • Schema Design and Normal Forms: Reducing redundancy in the database
  • Physical Database Design: Tuning your database for performance