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Chapter 5

0. Chapter 5. Relationships & Queries in Databases. Types of Relationships. One to One Examples? Analysis Technique Consider ThingA and ThingB Can ThingA be related to more than one ThingB? Can ThingB be related to more than one ThingA?

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Chapter 5

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  1. 0 Chapter 5 Relationships & Queries in Databases

  2. Types of Relationships One to One • Examples? • Analysis Technique • Consider ThingA and ThingB • Can ThingA be related to more than one ThingB? • Can ThingB be related to more than one ThingA? • If the two answers are NO, then it is a one to one relationship.

  3. Types of Relationships One to Many • Examples? • Analysis Technique • Consider ThingA and ThingB • Can ThingA be related to more than one ThingB? • Can ThingB be related to more than one ThingA? • If the answers are no and yes, or yes and no, then the relationship is one to many.

  4. Types of Relationships Many to Many • Examples? • Analysis Technique • Consider ThingA and ThingB • Can ThingA be related to more than one ThingB? • Can ThingB be related to more than one ThingA? • If the answers are yes and yes, then you have a many to many relationship

  5. Leads to Serious Data Redundancy Hierarchical

  6. Hierarchical

  7. Network

  8. Difficult to manage and implement relationships Network

  9. The most popular structure Relational

  10. Relational

  11. Find the name and hire date of the manager working on the sales manual project

  12. Schemas Schema - A description of the database Subschema – describes a subset of the database and which users have access to this subset

  13. Data Definition Language • Language Used to describe Schemas and Subschemas • Describes relationships between different data • Provides a Logical view of the data

  14. Data Dictionary Entry • A more detailed description of the data in a database • Specifies data types and ranges • Assists programmers in understanding the data

  15. Logical vs. Physical Access Paths • Database Management Systems concentrate on Physical access to the underlying tables • Concurrency control • Query’s • Creating/deleting tables • MIS systems are often software packages that (Logically) interface with a DBMS • monthly reports • charts • automated inquiries

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