Database Foreign Key Constraints

Study Notes

Foreign Key Constraint

A foreign key in a database table, also known as a referential integrity constraint, acts as a link between two tables
It references a primary key in another table
Foreign keys can have duplicate values and be set to NULL (meaning no reference).
A single table can have multiple foreign keys.

Example Table Structure

The DEPT table contains the department ID (DEPTID) as the primary key and the department names (DNAME).
The EMPLOYEE table contains employee IDs (empld), employee names (Name) and a department field (Dept) acting as the foreign key.
The Dept column in EMPLOYEE references the DEPTID column in the DEPT table, ensuring that each employee is associated with a valid department.

Database Relationship

The diagram illustrates the relationship between two tables based on the foreign key constraint.
It shows a "CHILD TABLE" and "PARENT TABLE".
The "CHILD TABLE" (EMPLOYEE) contains the foreign key which references the primary key in the "PARENT TABLE" (DEPT).
The relationship is visualised with an arrow pointing from the CHILD TABLE to the PARENT TABLE.

Training Session

This document is likely part of a training session for database systems like MySQL.
The training material includes slides and diagrams.
The presentation includes specific sections focusing on the EMPLOYEE and DEPT tables as an example.

Description

This quiz covers the concept of foreign key constraints in databases, including their role in establishing relationships between tables. It discusses how foreign keys can reference primary keys, their implications on data integrity, and the structure of related tables using examples. Test your knowledge on foreign keys and their importance in database design!