Database systems design implementation and management ninth edition answers

These relations are based on algebraic set theory. However, the user perceives the relations to be tables.

Tables, also called relations, are related to each other by sharing a common entity characteristic. Tables are especially useful from the modeling and implementation perspecectives. Because tables are used to describe the entities they represent, they provide ane asy way to summarize entity characteristics and relationships among entities. And, because they are purely conceptual constructs, the designer does not need to be concerned about the physical implementation aspects of the database design.

What is a relational diagram? Give an example. Therefore, it is easy to see what the entities represent and to see what types of relationships , 1:M, M:N exist among the entities and how those relationships are implemented. What is logical independence? Logical independence exists when you can change the internal model without affecting the conceptual model.

Within the database environment, a data model represents data structures and their characteristics, relations, constraints, and transformations. As its name implies, a purely conceptual model stands at the highest level of abstraction and focuses on the basic ideas concepts that are explored in the model, without specifying the details that will enable the designer to implement the model.

For example, a conceptual model would include entities and their relationships and it may even include at least some of the attributes that define the entities, but it would not include attribute details such as the nature of the attributes text, numeric, etc.

In the text, the term database model is be used to refer to the implementation of a data model in a specific database system. What is physical independence? You have physical independence when you can change the physical model without affecting the internal model.

Therefore, a change in storage devices or methods and even a change in operating system will not affect the internal model. The terms physical model and internal model may require a bit of additional discussion:.

The physical model operates at the lowest level of abstraction, describing the way data are saved on storage media such as disks or tapes. The physical model requires the definition of both the physical storage devices and the physical access methods required to reach the data within those storage devices, making it both software- and hardware-dependent.

The storage structures used are dependent on the software DBMS, operating system and on the type of storage devices that the computer can handle. An internal schema depicts a specific representation of an internal model, using the database constructs supported by the chosen database. What is connectivity? ERD modelers use the term connectivity to label the types of relationships.

Database modelers use the term connectivity to label the minimum and maximum number of entity occurrences for each entity in a relationship. Commonly, the connectivities are written within parentheses. Thus the connectivity for the relationship is 1,1 , for the 1:M relationship it is 1,M , and for the M:N relationship it is M,N.

This short line segment is drawn at a degree angle to the relationship line. Problem Solutions Use the contents of Figure 2. But each customer has only one agent. Therefore, the business rules may be written as follows: One agent can have many customers. Each customer has only one agent. Chapter 2 Data Models 2. For discussion purposes, you might use the Chen model shown in Figure P2. Compare the two representations of the business rules by noting the different ways in which connectivities 1,M are represented.

The OO model is shown in Figure P2. The DealCo relational diagram shows the initial entities and attributes for the DealCo stores, located in two regions of the country. Figure P2. Identify each relationship type and write all of the business rules. One region can be the location for many stores. Each store is located in only one region.

Each store employs one or more employees. Each employee is employed by one store. In this case, we are assuming that the business rule specifies that an employee cannot work in more than one store at a time. A job — such as accountant or sales representative -- can be assigned to many employees. For example, one would reasonably assume that a store can have more than one sales representative. Each employee can have only one job assignment.

In this case, we are assuming that the business rule specifies that an employee cannot have more than one job assignment at a time. Chapter 2 Data Models 5. The Chen model is shown in Figure P2. As you examine the Table P2. All of the relationships are 1:M. One course can generate many classes. Each class is generated by one course. One class can be referenced in enrollment many times. Each individual enrollment references one class. A student cannot enroll in the same class more than once.

If a student enrolls in four classes, that student will appear in the ENROLL entity four times, each time for a different class. One student can be shown in enrollment many times. Chapter 2 Data Models 8. Create the UML class diagram that reflects the entities and relationships you identified in the relational diagram. Typically, a patient staying in a hospital receives medications that have been ordered by a particular doctor.

Each medical order is written for a single patient. Each medication can be prescribed in many orders. Each medical order can prescribe many medications. UBA maintains a small network database to track painters, paintings, and galleries. A painting is painted by a particular artist, and that painting is exhibited in a particular gallery. A gallery can exhibit many paintings, but each painting can be exhibited in only one gallery.

Similarly, a painting is painted by a single painter, but each painter can paint many paintings. What tables would you create, and what would the table components be? We would create the three tables shown in Figure P2. For example, if a painter has painted six paintings, two may be exhibited in one gallery, one at another, and three at the third gallery.

Naturally, if galleries specify exclusive contracts, the database must be changed to reflect that business rule. The last business rule reflects the fact that a painting can be physically located in only one gallery at a time.

If the painter decides to move a painting to a different gallery, the database must be updated to remove the painting from one gallery and add it to the different gallery. How might the independent tables be related to one another?

Using the ERD from Problem 10, create the relational schema. Create an appropriate collection of attributes for each of the entities. Make sure you use the appropriate naming conventions to name the attributes. The relational diagram is shown in Figure P2. Each sales representative writes many invoices.

Each invoice is written by one sales representative. Each sales representative is assigned to one department. Each department has many sales representatives. Each customer can generate many invoices. Each invoice is generated by one customer. Note that a 1:M relationship is always read from the one 1 to the many M side.

Note that the ERD reflects some simplifying assumptions. For example, each book is written by only one author. Each book is published by one publisher. A publisher can submit many book contracts. Each book contract is submitted by one publisher.

One author can sign many contracts. Each contract is signed by one author. One author can write many books. Each book is written by one author.

This ERD will be a good basis for a discussion about what happens when more realistic assumptions are made. For example, a book — such as this one — may be written by more than one author. Therefore, a contract may be signed by more than one author. Your students will learn how to model such relationships after they have become familiar with the material in Chapter 3. Each of those departments has many employees assigned to it, but each employee works for only one department.

Problem 10RQ. Problem 11RQ. Problem 12RQ. Problem 13RQ. Problem 14RQ. Problem 15RQ. Problem 16RQ. Problem 17RQ. Problem 1P. Problem 4P. Problem 5P. Problem 6P. Problem 7P. Problem 8P. Problem 9P. Problem 10P. Problem 11P. See examples below:. Data: Data is set of variables which are used for describing specific topic. It can be meaningless Importance of Data Models: The main function of a data model is that they help to understand Difference between database and table: The differences between database and table are mentioned Conditions: Following are the conditions should be met before an entity is referred as a weak Entity Supertype: The entity supertype is an entity type that has the relation with one or more Normalization: The process used to minimize data redundancy and dependency in a relational database That is, Entity integrity: When creating a table, the primary key in the table must be assured and the Information system: A system that is designed in transforming the data into information is called as Business Intelligence BI : Business intelligence defines applications, technologies and practices Big Data: The term big data refers to the vast amount of data which cannot be processed and analysed Database Connectivity and uses: Database connectivity includes the application programs used for More Editions of This Book Corresponding editions of this textbook are also available below:.

Database Systems. Database Systems: Design, Implementation, and Management.