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Database Organization and Design

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

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

  2. 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

  3. 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

  4. 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.

  5. Levels of Abstraction View 1 View 2 View 3 Conceptual Schema Physical Schema

  6. 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

  7. 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

  8. 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

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