Understanding Database Relationships: Employee and Department Tables

The question asks about the specific database concept used to link two different tables, specifically the 'Employee' table and the 'Department' table. We are given the structures of these tables:

• Employee Table: Contains columns like ID, name, Address, Phone, and Deptno.
• Department Table: Contains columns like Deptno and Dname.

The common column, 'Deptno', present in both tables is the key to establishing a connection or relationship between an employee and their respective department.

Database Keys Explained

Let's look at the different types of keys mentioned in the options to understand why one is correct:

• Primary Key: A column (or set of columns) that uniquely identifies each record within a table. For example, 'ID' in the Employee table is likely a primary key. 'Deptno' might be the primary key in the Department table.
• Candidate Key: Any column or set of columns that *could* serve as a primary key because it uniquely identifies records. Both 'ID' and potentially 'Deptno' (if unique in Employee) could be candidate keys for the Employee table.
• Alternate Key: A candidate key that was not chosen as the primary key. If 'Deptno' uniquely identified employees but 'ID' was chosen as the primary key, then 'Deptno' would be an alternate key.
• Foreign Key: A column (or set of columns) in one table that refers to the primary key (or another unique key) in another table. It creates a link between the two tables and ensures referential integrity (meaning you can't have an employee assigned to a department that doesn't exist).

Identifying the Linking Mechanism

In this scenario, the 'Deptno' column in the 'Employee' table points to the 'Deptno' in the 'Department' table. This is exactly the function of a Foreign Key. The 'Deptno' in the Employee table is referencing the primary key ('Deptno') of the Department table, thereby representing the relationship: each employee belongs to a specific department.

Therefore, the Foreign Key is used to represent the relationship between the Employee and Department relations.