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Questions and Answers
What is the main objective of the Logical Database Design phase?
To translate the conceptual data model into a logical data model for the data requirements of the enterprise.
What is typically represented by a relation in the relational model?
What is the formal term for rows in the relational model?
Tuples
What do we call the unique identifier for each row in a relation?
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In the relational model, what is an attribute?
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What is the example provided for a relation name in the context of CUSTOMER?
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A tuple is an ordered set of values enclosed in ______.
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What is an example domain provided in the document for valid values?
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Study Notes
Relational Model Concepts
- A relation is like a table of values.
- Each row in the table represents a real-world entity or relationship.
- Rows in the formal model are called tuples.
- Each column has a column header that explains the data.
- In the formal model, column headers are called attributes.
- Each row in the table is uniquely identified by a data item (or set of items) called the key.
Formal Definitions - Schema
- The Schema (or description) of a Relation is denoted by R(A1, A2, ... , An).
- R is the relation name, and A1, A2, ... , An are the attributes of the relation.
- For example, a relation named CUSTOMER could have these attributes: Cust-id, Cust-name, Address, Phone #.
- Each attribute has a domain, which is a set of valid values.
- For example, the domain of Cust-id might be 6-digit numbers.
Formal Definitions - Tuple
- A tuple is an ordered set of values, enclosed in angled brackets.
- Each value is derived from an appropriate domain.
- A row in the CUSTOMER relation is a 4-tuple, with four values, for example: <123456, John Smith, 123 Main St., (555) 123-4567>.
- A relation is a set of tuples (rows).
Formal Definitions - Domain
- A domain has a logical definition. For example, "USA_phone_numbers" is the set of 10-digit phone numbers valid in the USA.
- Domains also have a data-type or a format defined. For example, USA_phone_numbers could have the format (ddd)ddd-dddd, where each d is a decimal digit.
- Dates have various formats, such as yyyy-mm-dd or dd-mm-yyyy.
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Description
Test your knowledge on the essential concepts of the relational model, including relations, tuples, and schemas. This quiz will help you understand how data is structured in tables and the significance of keys and attributes. Perfect for students learning database management.
