Looking for:
Fundamentals of database systems 6th edition solution manual free download |
Informations du document - Fundamentals of database systems 6th edition solution manual free download
Some database professionals believe that it is best to use keys that are uniquely generated by the database, for example each row may have a primary key that is generated in the sequence of creation of rows tuples.
There are many advantages and disadvantages that are often been argued in design sessions. The main advantage is that it gives us an invariant key without any worries about choosing a unique primary key. Some database designers are reluctant to use generated keys also known as surrogate keys for primary keys such as StudentID because they are artificial.
Suppose that you were able to guarantee uniqueness of a natural key that included last name. Are you guaranteed that the last name will not change during the lifetime of the database? If the last name last name can change, what solutions can you propose for creating a primary key that still includes last name but remains unique? What are the advantages and disadvantages of using generated surrogate keys? By keeping the name attributes separated, we allow the possibility of looking these pieces of their name.
In a practical use, it is not likely that the user will know the correct primary key for a given student and so we must consider how a user will locate the correct row without this information.
Therefore, a practical system should allow name searches by FirstName and LastName; we must leave MiddleInitial separated still to avoid ambiguities from combining these pieces together.
A single attribute Phone would no longer suffice if a student were able to have multiple phone numbers. We could possibly have multiple rows for a single student to allow this to happen, but then we have violated key principles of database design e.
A better solution would be to include the additional attributes HomePhone, CellPhone, and OfficePhone and allow the possibility of these attributes to have no value. Smap Comp. Carl Hamacher Computer Organization 5th Edition. Install Radiance.
Teradata Application Dev4. Basic Rdbms Oracle. Lab Manual. Isu Tables. Tableau Visual Analytics. Mobile Workforce Analytics Ds Update Dbtab. Energy Accounting 1. Lecture 1. AI For Engineering. Views Downloads 55 File size 74KB. Excerpts from this work may be reproduced by instructors for distribution on a not-for-profit basis for testing or instr. Our nationwide network. What type of applications would each user need?
To which user category would each belong and what type of interface would they need? Answer: a Registration Office User: They can enter data that reflect the registration of students in sections of courses, and later enter the grades of the students. Applications can include: - Register a student in a section of a course - Check whether a student who is registered in a course has the appropriate prerequisite courses - Drop a student from a section of a course - Add a student to a section of a course - Enter the student grades for a section Application programmers can write a number of canned transactions for the registration office end-users, providing them with either forms and menus, or with a parametric interface.
Rodney Topor. Michael Lawley. We present a proposed query language for extended entity relationship schemas. The language improves on previous proposals by using only concepts explicitly in a given schema. It includes quantiers and aggregates to allow complex queries to be expressed, and it allows derived subtypes, attributes and relation- ships to be dened and used in queries.
Further extensions are discussed. Modeling temporal database over relational database using 1NF model is considered the most popular approach. This is because of the easy implementation as well as the modeling and querying power of 1NF model. In this paper, we compare a new approach for representing valid-time temporal database in terms of structure and performance to the main models in literature with attribute and tuple timestamping.
The measurement of the performance is represented by the processing time to get the required temporal data as well as the size of the whole stored temporal data. A test has been performed by running sample queries for the same data in the represented models.
❿
No comments:
Post a Comment