What is a NULL Value?

Here's an example to illustrate the concept of NULL value:

CREATE TABLE Employees (
  EmployeeID INT,
  EmployeeName VARCHAR(50),
  Salary DECIMAL(10,2),
  Department VARCHAR(50)
);

INSERT INTO Employees (EmployeeID, EmployeeName, Salary, Department)
VALUES
  (1, 'John Doe', 5000, 'IT'),
  (2, 'Jane Smith', NULL, 'HR'),
  (3, 'Michael Johnson', 7000, NULL);

In the above example, the "Employees" table has four columns: EmployeeID, EmployeeName, Salary, and Department. In the second and third records, the Salary and Department columns have NULL values.

NULL values are different from empty strings or zeros. An empty string ('') or zero (0) represents a valid value, whereas a NULL value indicates the absence of any specific value.

When dealing with NULL values, it's essential to handle them appropriately in SQL queries using functions like IS NULL or IS NOT NULL to check for the presence or absence of NULL values.

NULL values play a crucial role in handling missing or unknown data in database tables. Understanding their nature and handling them correctly is essential for accurate data manipulation and retrieval.

Demo Database Table: Employees

EmployeeID	EmployeeName	Salary	Department
1	John Doe	5000	IT
2	Jane Smith	(NULL)	HR
3	Michael Johnson	7000	(NULL)

This is a demo database table called "Employees" that demonstrates the usage of NULL values. Customize the content and structure of the table to match your specific requirements.