Primary Key Quiz: Define Foreign Keys in Relational Database

10 Questions

What is the purpose of a primary key in a database table?

To uniquely identify each row in the table

What is the difference between a single-column primary key and a composite primary key?

A single-column primary key consists of one column, while a composite primary key consists of multiple columns

What is the purpose of a foreign key in a database table?

To establish a relationship between two tables

What is the concept of referential integrity in a database?

It ensures that a foreign key value always matches a primary key value in another table

What happens if a primary key value is changed in the parent table?

The primary key change will not be allowed due to referential integrity constraints

Which statement accurately describes referential integrity?

It ensures that a foreign key value must reference an existing primary key value in the referenced table.

What is the implication of the rule 'Do not delete data required by another table' in the context of referential integrity?

A primary key value cannot be deleted if it has corresponding foreign key values in related tables.

Which statement accurately describes the rule 'Do not add incompatible data to a child table' in the context of referential integrity?

It ensures that foreign key values added to a table must reference existing primary key values in the referenced table.

What is the significance of the relationship between primary keys (PK) and foreign keys (FK) in the context of referential integrity?

A primary key can have multiple foreign keys referencing it from different tables.

Which statement accurately describes the relationship between primary keys (PK) and foreign keys (FK) in the context of referential integrity?

A foreign key value must reference an existing primary key value in the referenced table.

Study Notes

Primary Key

A primary key is a column or combination of columns in a table that uniquely identifies a row in the table.
A primary key column cannot contain a NULL value or an empty string.
A primary key value must be unique within the entire table.
A primary key value should not be changed over time.

Types of Primary Key

Single Primary Key: Consists of one column.
Composite Primary Key: Consists of a combination of columns.

Foreign Key

A foreign key is a column in a table that refers to the Primary Key in another table.
The column in the 'Child' table refers to the column in the 'Parent' table.
The 'Parent' table is the table that contains the Primary Key.
The 'Child' table is the table that contains the Foreign Key.

Referential Integrity

A database concept that builds and maintains logical relationships between tables to avoid logical corruption of data.
Made up of the combination of a Primary Key and a Foreign Key.
Does not allow adding a record in a table that contains a Foreign Key unless the reference table contains a corresponding Primary Key.
Two specific database rules must exist between tables:
- Do not delete data required by another table.
- Do not add incompatible data to a child table.

Rules of Referential Integrity

Do not delete a Primary Key if it has dependencies (Foreign Key related to it).
Value of a Foreign Key must exist in the Primary Key it refers to.
Check that there are no records in related tables that require the record being deleted.

Database 1 Lab: Introduction to Primary Key