Provides a set of interview questions and answers to access the technical knowledge and characteristics of candidates applying for a position as a Web site designer.
Additionally, Oracle data file internals are considered and how to use multiple data block sizes to detect and repair Oracle data segment bottlenecks and segment waits is described. Provides a set of interview questions and answers to access the technical knowledge and characteristics of candidates applying for a webmaster position.
Looks at the interview process, provides possible interview questions, and includes the best answers for job seekers. The evolution of Oracle has led to a revolution in design practices. For Oracle 10g, database physical structures have become more complex than ever before and database designers face multiple ways to implement their logical models. IS students studying database design and administration need to be able to implement management systems in a way that.
Beylebooks Download PDF full books, magazine dan comics. Analytical aptitude - keep in mind the broad goals even while poring over the smallest details. Conceptual Design Methodology 1. Define the problem and define database objectives 2.
Analyze current database, assess user requirements, and create data model 3. Design data structures tables, fields, field specifications, establish keys 4. Establish table relationships 5. Clarify business rules critical to database design e.
Determine and establish user views of data 7. Review data integrity and reiterate design methodology. Statement of Purpose 1. Declare a specific purpose for the database to focus and guide its development. We need to maintain complete entertainer information. We need to maintain complete customer information.
We need to track all customer-entertainer bookings. We need to maintain financial records of both payments from customers and payments to entertainers. Assessment of User Requirements: Specific requirements Goals of analysis of user requirements: collect a list of business goals, entities to track, a database schema, and sample report outputs.
What characteristics describe each object? What unique characteristic distinguishes each object from other objects of the same type? How do you use this data e. Over what period of time are you interested in this data? Are all instances of each object the same? What events occur that imply associations between various objects?
Is each activity or event always handled the same way or are there special circumstances? A model is a simplified representation usually a graphic of a complex object in reality to make it understandable If the elements in the model are correctly associated with elements in reality, the model can be used to solve problems in reality e. Representation of data in a simplified fashion that makes it understandable Once established, database design is relatively straightforward.
Something that can be identified in the users environment about which we want to store data; typically is a noun Entities or objects must have occurrences that can be uniquely identified Identified by an organization or its users Consists of tangible or intangible objects or events.
Each entity occurrence has a unique identifier The identifier is an attribute or group of attributes that describes or identifies each entity occurrence An identifier should be unique to each occurrence Referred to as a primary key in relational models.
Degree of Relationship: Binary In a binary relationship, two entities are associated. This is the most common degree of relationship. Degree of Relationship: Ternary In a ternary relationship, three entities are associated.
Degree of Relationship: Unary Recursive In a recursive relationship, one entity is associated with itself. Connectivity describes constraints on relationship also referred to as maximum cardinality Number of instances of entity B that can or must be associated with each instance of entity A.
M:N relationships are represented by two 1:M relationships. Cardinality is the specific number of entity occurrences associated with one occurrence of the related entity often referred to as business rules because cardinality is usually determined by organizational policy.
A toy may not be borrowed by anyone, or it may be borrowed by one child. Occurrences Diagram Pictorial mapping of the occurrences between two entities assists in understanding connectivity and cardinality. One child may rent many toys 1:M. Relationship Participation Also referred to as minimum cardinality Mandatory Participation An instance of a given entity must definitely match an instance of a second entity e. First step - develop a list of entities and attributes that are of interest to the enterprise.
E-R Design consists of determining entities, attributes, relationships, relationship types, level of participation in relationships, identifiers, and then drawing an E-R Diagram. E-R Diagram model is a blueprint from which a well-structured database is created. Steps in Entity-Relationship Modeling 1. Identify entities 2. Identify relationships 3. Determine relationship type 4.
Determine level of participation 5. Assign an identifier for each entity 6. Draw completed E-R diagram 7. Deduce a set of preliminary skeleton tables along with a proposed primary key for each table using rules provided 8.
Develop a list of all attributes of interest not already listed and systematically assign each to a table in such a way to achieve a 3NF design i. Each book is written by how many authors? Each author writes how many books? Each book may be authored by zero anonymous , one, or more than one author and each author may write zero, one, or more than one book.
The relationship type is many-to-many or:. Since each book does not have to be authored anonymous and since each author does not have to write a book may make CD the level of participation is optional for both sides of the relationship of AUTHOR-writes-BOOK combination. A database is to be set up to record information about faculty, the courses they teach, and the students who take courses. Some courses are taught by teams of faculty members. Each faculty member teaches how many courses?
Each course is taught by how many faculty? Each student takes how many courses? Each course is taken by how many students? We are told some courses are taught by zero, one, two, or three faculty. This is a many-to-many relationship. This too is a many-to-many relationship. You are now told that in addition to the relationships given, each student is assigned a faculty advisor who gives direction in choosing courses.
Use occurrences diagram to visualize relationship between entities We are told each student is advised by exactly one faculty advisor. We can assume that each faculty member advises zero, one, or more students. This means the additional relationship is of type one-to-many or 1:M. Using data models to conceptualize the design of a database saves time and money because a completed E-R diagram is the actual blueprint of the database.
Its composition must reflect an organization's operations accurately if the database is to meet that organization's data requirements. The completed E-R diagram also lets the designer communicate more precisely with those who commissioned the database design.
Its easier to correct design flaws at the data modeling stage. Do not confuse entities and relationships with actual tables. The transformation or decomposition of E-R models will be discussed within the next few weeks. E-R modeling is an iterative process. Even when complete, ER models generally do not provide a complete picture e.
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Flag for inappropriate content. Download now. For Later. Related titles. Carousel Previous Carousel Next. Jump to Page. Search inside document. A good database is the foundation for good applications. Database Models Two Categories of Database Models Conceptual models focus on the logical nature of the data representation. Database Models Relational database Codd, E. Database Models E-R model is commonly used to: Translate different views of data among managers, users, and programmers to fit into a common framework.
Database Models Three Types of Relationships One-to-many relationships 1:M A painter paints many different paintings, but each one of them is painted by only that painter.
Keys Controlled redundancy shared common attributes makes the relational database work. Indexes An index is composed of an index key and a set of pointers.
Form- data entry 3. Query- asks questions 2. Menu - organizes components 5. The logical view allows a simpler file concept of data storage. The use of logically independent tables is easier to understand.
What is Relational Database Design? Why use a Relational Data Model Design? Database Design Problems Multi-valued problems e. Database Design Problems Deletion anomalies What happens if we delete all the book entries for a given publisher? Impartiality - find best solution Relax constraints - assume anything is possible Pay attention to details and definitions Reframing - iteratively analyze in new way - be creative! A good designer combines the art of design with the science of design.
Declare a specific purpose for the database to focus and guide its development e. Assessment of User Requirements: What is analyzed? Determine relationship type. Ask: Each book is written by how many authors?
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