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Database Organization and Design. Chapter 1 Adapted from slides by Raghu Ramakrishnan, raghu@cs.wisc.edu. 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 l.jpg

Database Organization and Design

Chapter 1

Adapted from slides by Raghu Ramakrishnan, raghu@cs.wisc.edu


What is a dbms l.jpg
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


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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


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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.


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Levels of Abstraction

View 1

View 2

View 3

Conceptual Schema

Physical Schema


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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


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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


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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