Relational Databases (Leaving Cert Computer Science): Flashcards
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Relational database definition
Relational database definition
Database storing & providing access to related data points
Primary key definition
Primary key definition
Unique identifier for each record in a database table
Primary key uniqueness characteristic
Primary key uniqueness characteristic
Must be unique for each row in the table
Primary key non-null characteristic
Primary key non-null characteristic
Cannot contain null values; every record must have a value
Primary key immutability characteristic
Primary key immutability characteristic
Should not change over time; stable and permanent
Composite primary key definition
Composite primary key definition
Primary key consisting of multiple columns combined
Why is full name unsuitable as primary key?
Why is full name unsuitable as primary key?
Multiple people may have the same name (not unique)
Foreign key definition
Foreign key definition
Column(s) that creates a link between data in two tables
What does a foreign key reference?
What does a foreign key reference?
Primary key in another table
Can a primary key also be a foreign key?
Can a primary key also be a foreign key?
Yes, a primary key can also be a foreign key
Student Table primary key example
Student Table primary key example
ID column (uniquely identifies each student)