Podcast
Questions and Answers
A single alphabetic, numeric, or other symbol is known as a ________.
A single alphabetic, numeric, or other symbol is known as a ________.
character
What does a field or data item represent?
What does a field or data item represent?
attribute
Give an example of a record.
Give an example of a record.
payroll record with name, SSN, pay rate
Define a file or table in terms of data.
Define a file or table in terms of data.
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What is a database?
What is a database?
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Which of the following are common database structures? (Select all that apply)
Which of the following are common database structures? (Select all that apply)
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Which type of database structure is most widely used?
Which type of database structure is most widely used?
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What is the main characteristic of a hierarchical database structure?
What is the main characteristic of a hierarchical database structure?
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Which operation in a relational database creates a subset of records based on a stated criterion?
Which operation in a relational database creates a subset of records based on a stated criterion?
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Study Notes
Logical Data Elements
- A character is a single alphabetic, numeric, or other symbol.
Data Elements
- A field or data item represents an attribute (characteristic or quality) of an entity (object, person, place, event).
- Examples of fields or data items include salary and job title.
Records
- A record is a grouping of all the fields used to describe the attributes of an entity.
- Example: a payroll record with name, SSN, and pay rate.
Files or Tables
- A file or table is a group of related records.
Databases
- A database is an integrated collection of logically related data elements.
Database Structures
- Common database structures include:
Types of Database Structures
- Hierarchical
- Network
- Relational
- Object-oriented
- Multi-dimensional
Database Structures
- Common database structures include Hierarchical, Network, Relational, Object-oriented, and Multi-dimensional.
Hierarchical Structure
- An early DBMS structure where records are arranged in a tree-like structure.
- Relationships are one-to-many.
Network Structure
- Used in some mainframe DBMS packages.
- Supports many-to-many relationships.
Relational Structure
- The most widely used structure.
- Data elements are stored in tables.
- A row represents a record, while a column is a field.
- Allows relating data in one file with data in another, if both files share a common data element.
Relational Operations
- Select: Create a subset of records that meet a stated criterion, e.g., employees earning more than $30,000.
- Join: Combine two or more tables temporarily, creating a single table that looks like one big table.
- Project: Create a subset of columns in a table.
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Description
Learn about the basics of data elements, records, and files in logical data structures. Understand the concepts of characters, fields, and tables.
