Flashcards
Database and Web application design
Flashcards do conjunto (29)
- 1What are the 9 steps of the Connolly and Beggs method for mapping ERDs to a database?1. Strong Entities
2. Weak Entities
3. 1 to many relationships
4. 1 to 1 recursive
5. (ignore for 8 steps) 1 to 1o binary
6. Superclass and Subclasses
7. Many to many relationships
8. Complex relations
9. Multi-valued attributes - 2What is the conceptual model?It is a way of documenting the initial ideas of the database/business. It should have entities and relationships but at a very high level
- 3What is the logical model?The logical model is a representation of teh entities, relationships, attributes with primary and foriegn keys identified.
- 4What is the physical model?The physical model would be able to be implemented directly as a database. It would contain attribute types and everything should have been fixed properly so that entities have become tables etc reay to be implemented
- 5Why use normalisation?NOrmalisaion is the process of organising data into tables to avoid redundancy
- 6What step should be completed in 1NF?Remove the repeating group
- 7What step should be completed in 2NF?Remove partial dependencies (dependencies that rely on a primary key)
- 8What step should be taken to complete 3NF?Remove the transitive dependencies (dependencies that don't rely on the primary key)
- 9WHat steps would you take to complete BCNF?Remove functional dependency abnormalities.
Identify all dependencies in a table. Each determinant should be a candidate key. - 10What is an entity?Something significant to the business.
Usually a noun.
It will later become a table in the database - 11What is an attribute?Describes an entity.
Represents something of significance to the business. - 12What is an atomic attribute?A singular attribute. An attribute that can only hold a single value
- 13What is a multi-valued attribute?An attribute that can have more than one value such as an address. This should be split up into different atomic attributes in step 9 of the 9 step method.
- 14What is a derived attribute?A derived attribute is an attribute thats value is taken from another attribute (e.g. age could be taken from DOB.)
- 15What are volitile and non volitile attributes?Volitile means that the attribute value is likly to change. (e.g. age)
Non volatile means that they are not likly to change(e.g. DOB)
Non volitile attributes should be use if they can and derived attributes should be used if necessary - 16What is a composite attribute?Composed of multi-valued attributes of which each can be independant. e.g. address can be broken down
- 17What is a complex attribute?A complex attribute is both multi valued and composite
- 18What are the goals in Entity Relationship Modeling?1. Capture required information
2. Ensure information only appears once
3. Locate information in a predictable logical place - 19What is the degree or cardinality of a relationship?It is how the entities link to eachother. e.g. 1 to many
- 20What is a recursive relationship?A relationship that links one entity to the same entity. Also known as a unary relationship.
- 21What is a ternary relationship?When 3 entities are linked to eachother. (e.g. a staff member at a college may register a student. This would be represnted as 3 entities called staff, student and college)
- 22What are business rules?They are the rules of tjhe business. They represent aspects of the business that include optionality and cardinality (e.g. a STUDENT must enroll on a SUBJECT)
The capial lettered words represent the entity. - 23What would make a relationship redundant?When a relationship can be derived from another relatioship in the model. e.g.
If there are 3 entities 1 2 and 3.
1 and 2 are linked
2 and 3 are linked
so a relationship between 1 and 3 would be redundant. - 24What is CRUD?Create, Read, Update, Delete.
These represent the functions of a database. - 25What is CRUD analysis?It is an analysis technique to determine where data may be Created, read, updated or deleted in the website. A CRUD matrix is used to determine this.
- 26What is a EERD?Enhanced Entity Relationship Diagram. It may include inheritance and use UML notation.
- 27What are the 2 types of business rules?1. Structural
2. Procedural - 28What is a structural business rule?It indicates the types of information to be stored and how they relate. Can nearly always be documented in an ERD
- 29What is a procedural business rule?A part of the business that includes workflow or process related. Can't be diagramed in an ERD but must be documented.(kinda like a non functaional requirement
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- Degree Database and Web applications FlashCards sobre Database and Web application design, criado por elbruce em 08-12-2013.
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