Podcast
Questions and Answers
What is a primary key?
What is a primary key?
A candidate key is always a primary key.
A candidate key is always a primary key.
False
What is a composite key?
What is a composite key?
A key defined by more than one column.
A __________ key is a field linked to another table's primary key field.
A __________ key is a field linked to another table's primary key field.
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What does referential integrity ensure?
What does referential integrity ensure?
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Match the following terms with their definitions:
Match the following terms with their definitions:
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Referential integrity allows the deletion of a primary key if there are associated foreign keys in other tables.
Referential integrity allows the deletion of a primary key if there are associated foreign keys in other tables.
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Provide an example of a candidate key.
Provide an example of a candidate key.
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Study Notes
Primary Key
- A primary key is a unique identifier for a table, consisting of one or more columns.
- Candidate keys can guarantee uniqueness but are not necessarily primary keys until specified.
- Example: A user table may have a unique userid as the primary key and a unique email address as a candidate key that is not designated as the primary key.
Composite Key
- A composite key consists of multiple columns used to define a primary key.
Foreign Key
- A foreign key is a column that creates a link to another table's primary key, establishing a relationship between two tables.
Referential Integrity
- Referential integrity ensures the accuracy and consistency of data across related tables.
- This is maintained by ensuring that foreign key values reference valid and existing primary key values in the parent table.
- Example: In the Chinook database, each Customer's SupportRepId is a foreign key linked to the EmployeeId in the Employees table.
- Deleting or changing an EmployeeId without corresponding updates to SupportRepId would compromise database integrity, potentially leading to Customers with invalid or missing SupportRepId entries.
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Description
This quiz covers key concepts related to primary keys, composite keys, foreign keys, and the principle of referential integrity in relational databases. Understanding these elements is crucial for maintaining data integrity and establishing relationships between tables in a database. Test your knowledge and ensure your comprehension of these fundamental aspects of database management.
