If a relationship exists among three or more entities, then:
A) recursive relationships must be established through the use of recursive foreign keys
B) a separate relation with a primary key that is the composite of the primary keys of each of the participating entities is created
C) separate relations are established for each class and for each of the subclasses
D) use the primary key of relation A as a foreign key in relations B and C
Answer: B
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Information Analysis Chapter 9
- Designing the database for an Internet-based electronic commerce application differs significantly from the process followed when designing the database for other types of applications.
- Multiple key retrieval is possible with the hashed file organization.
- Random key retrieval on the primary key is comparatively slow with the hashed file organization.
- Indexes should be used judiciously for databases that support transaction processing and other applications with heavy updating requirements.
- When using the sequential file organization, the addition of rows requires rewriting the file.
- A physical file is a named set of table rows stored in a contiguous section of secondary memory.
- Denormalization reduces the chance of errors introduced by normalizing relations.
- Generally speaking, a physical table corresponds to a relation.
- A null value is used to represent the zero digit in a relation.
- A derived field is a field that can be derived from other database fields.
- A relation is said to be in second normal form when there are no transitive dependencies.
- A relation is said to be in second normal form if the primary key consists of only one attribute.
- An attribute can be functionally dependent on more than attribute.
- Normalization is based on an analysis of weak entities.
- A relation is said to be in second normal form when its nonprimary key attributes do not depend on each other.
- Referencing a relation, the sequence of columns cannot be interchanged without changing the meaning or use of the relation.
- Each row of a relation corresponds to a record that contains data values for an entity.
- Object-oriented database models are the most frequently used database technologies for new information systems development.
- File and database design occurs in two steps.
- The index file organization:
- A field of data that can be used to locate a related field or row of data best describes:
- The process of splitting or combining normalized relations into physical tables based on affinity of use of rows and fields best describes:
- A named set of rows and columns that specifies the fields in each row of the table best describes:
- A single name that is used for two or more different attributes best defines:
- Merging relations is also referred to as: