A foreign key is a column (or a set of columns) that establishes a relationship between two tables by referencing the primary key of another table.

Example Usage:

sql

CREATE TABLE Departments (

DeptID INT PRIMARY KEY,

DeptName VARCHAR(50)

);

CREATE TABLE Employees (

EmpID INT PRIMARY KEY,

Name VARCHAR(50),

DeptID INT,

FOREIGN KEY (DeptID) REFERENCES Departments(DeptID)

);

DeptID in Employees is a foreign key, referencing DeptID in Departments.

Ensures referential integrity DeptID in Employees must exist in Departments.

Why Other Options Are Incorrect:

Option A (Super key) (Incorrect): A super key is any set of columns that uniquely identifies a row, but it does not reference another table.

Option B (Simple key) (Incorrect): A simple key is a single-column primary key, not a reference to another table.

Option C (Composite key) (Incorrect): A composite key consists of multiple columns but does not necessarily reference another table.

Thus, the correct answer is Foreign key, as it establishes a connection between two tables.