Search results
ntify the relationship between tables. There are three main types of keys, candida. e keys, primary keys and foreign keys. There is also an alternative key or secondary key that can be used, as the name suggests, as a secondary. tive key to the primary key.Super KeyA Super key is any combination of fields within a table that uniquely id.
- 458KB
- 4
Composite Key. If a table do have a single column that qualifies for a Candidate key, then you have to select 2 or more columns to make a row unique. Like if there is no EmployeeID or SSN columns, then you can make EmployeeName + DateOfBirth (DOB) as Composite Primary Key. But still there can be a narrow chance of duplicate rows.
Database System Concepts, 5th Ed. ©Silberschatz, Korth and Sudarshan See www.db-book.com for conditions on re-use. Chapter 7: Relational Database Design. Features of Good Relational Design Atomic Domains and First Normal Form Decomposition Using Functional Dependencies Functional Dependency Theory Algorithms for Functional Dependencies ...
- After learning the material in this chapter, you will be able to:
- Relational Terminology
- Relational database terminology
- Foreign Keys and Binary Relationships
- Extracting Data from a Relation
- EXAMPLE: GOOD READING BOOKSTORES
- EXAMPLE: WORLD MUSIC ASSOCIATION
- EXAMPLE: LUCKY RENT-A-CAR
- KEY TERMS
- EXERCISES
✔ Explain why the relational database model became practical in about 1980. ✔ Define such basic relational database terms as relation and tuple. ✔ Describe the major types of keys including primary, candidate, and foreign. ✔ Describe how one-to-one, one-to-many, and many-to-many binary relation-ships are implemented in a relational database. ✔ Desc...
In spite of the apparent conflict between non-redundant, linear file data storage and data integration demonstrated in the previous chapter, the concept of having the relative simplicity of simple, linear files or structures that resemble them in a true database environment is very desirable. After all, the linear file arrangement is the most basic...
Attribute (or Column or Field) Relation (or Table or File) Technical differences exist between the concept of a file and the concept of a relation (which is why we say that in a relational database the data only appears to be stored in structures that look like files). The differences include: The columns of a relation can be arranged in any order ...
Foreign Keys If in a collection of relations that make up a relational data-base, an attribute or group of attributes serves as the primary key of one relation and also appears in another relation, then it is called a foreign key in that other rela-tion. Thus Salesperson Number, which is the primary key of the SALESPERSON relation, is considered a ...
Thus far, the discussion has concentrated on how a relational database is structured, but building relations and loading them with data is only half of the story. The other half is the effort to retrieve the data in a way that is helpful and beneficial to the business organization that built the database. If the database management system did not p...
Figure 5.16 shows the relational database for the Good Reading Bookstores example that was described earlier in the book. Since publishers are in a one-to-many rela-tionship to books, the primary key of the PUBLISHER relation, Publisher Name, is inserted into the BOOK relation as a foreign key. There are two many-to-many rela-tionships. One, betwee...
Figure 5.17 shows the relational database for the World Music Association example that was described earlier in the book. There is a one-to-many relationship from orchestras to musicians and, in turn, a one-to-many relationship from musicians to degrees. Thus the primary key of the ORCHESTRA relation, Orchestra Name, appears in the MUSICIAN relatio...
Figure 5.18 shows the relational database for the Lucky Rent-A-Car example that was described earlier in the book. There is a one-to-many relationship from manufacturers to cars and another one-to-many relationship from cars to maintenance events. The former requires the manufacturer primary key, Manufacturer Name, to be placed in the CAR relation ...
Alternate key Attribute Attribute name Candidate key MANUFACTURER relation Manufacturer Name Manufacturer Country Sales Rep Name Sales Rep Telephone CAR Relation Car Serial Number Model Year Class Manufacturer Name MAINTENANCE relation Repair Number Car Serial Number Date Procedure Mileage Repair Time CUSTOMER relation Customer Number Customer Name...
The main relation of a motor vehicle registration bureau’s relational database includes the following attributes:I The relational Select operator. The relational Project operator. The relational Join operator. 13. Describe how the join operator works. Vehicle Identification Number License Plate Number Owner Serial Number Manu-facturer Model Year Co...
- 613KB
- 30
This second edition of Database Design book covers the concepts used in database systems and the database design process. Topics include: New to this edition are more examples, highlighted and defined key terms, both throughout and at the end of each chapter, and end-of-chapter review exercises. Two new chapters have been added on SQL, along ...
- Adrienne Watt
- 2nd Edition
A candidate key of an entity type is a minimal (in terms of number of attributes) superkey. For an entity type, several candidate keys may exist. During conceptual design, one of the candidate keys is selected to be the primary key of the entity type. Dept. of Computer Science UC Davis 2. Entity-Relationship Model
People also ask
Which key is selected during conceptual design?
Why is foreign key important in relational database?
What is a primary key?
What is a foreign key in a relation?
What is a key in a table?
What makes a good database design book?
7. Represent the User View As a Collection of Tables. • Step 1: Determine the entities involved and create a separate table for each type of entity • Step 2: Determine the primary key for each table • Step 3: Determine the properties for each entity • Step 4: Determine relationships between the entities. – One-to-many – Many-to-many ...
