Chapter 8 Notes
Unit 3 Database Management · Chapter 8
Appreciate Characteristics of a Database
Master relational database foundations: Limitations of Flat Files, Relational Terminology (Tuples, Attributes, Degree, Cardinality), and Relational Keys (Primary, Candidate, Alternate, Composite, Foreign).
Chapter 8 Theory
1. RDBMS Terminology & Architecture
Tuple / Record:A single horizontal row containing all values representing one entity.
Attribute / Field:A vertical column storing a specific category of data across records.
Degree vs Cardinality:Degree = Total count of columns.
Cardinality = Total count of rows.
Cardinality = Total count of rows.
2. Relational Keys in RDBMS
Primary Key:Uniquely identifies each record in a table. It can NEVER contain duplicate values and can NEVER be NULL.
Candidate Key & Alternate Key:All fields capable of being unique are Candidate Keys. The candidate keys that are not selected as the primary key are designated as Alternate Keys.
Composite Primary Key:A primary key formed by combining two or more columns together when no single column is unique.
Foreign Key:A field in a child table whose values reference the primary key of another parent table to establish relational links. Foreign keys CAN be duplicate and CAN be NULL.
Chapter 8 Practice
Solved MCQs: Database Characteristics & Keys
1
In Relational Database Management Systems (RDBMS), what do 'Degree' and 'Cardinality' refer to?
2
Which of the following database key types can NEVER contain NULL values and must uniquely identify each record?
3
When no single column is unique on its own, and two or more attributes are combined to uniquely identify a record, it is called a:
4
What is an 'Alternate Key' in database terminology?
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