NOT NULL constraint in SQL - Mini Project: Build & Apply

Using NOT NULL Constraint in SQL

📖 Scenario: You are creating a simple database table to store information about employees in a company. Each employee must have a unique ID and a name. The name cannot be empty because it is important to identify each employee.

🎯 Goal: Create a table called employees with two columns: id and name. The id column should be an integer and the primary key. The name column should be text and must not allow NULL values.

📋 What You'll Learn

Create a table named employees

Add an id column of type INTEGER as the primary key

Add a name column of type TEXT with a NOT NULL constraint

💡 Why This Matters

🌍 Real World

Ensuring important data fields like employee names are always filled in a company database.

💼 Career

Database developers and administrators use NOT NULL constraints to maintain data integrity and prevent missing critical information.

1

Create the employees table with id column

Write a SQL statement to create a table called employees with one column id of type INTEGER that is the primary key.

SQL

-- Create the employees table with id column
-- Your code here

Need a hint?

Use CREATE TABLE employees and define id INTEGER PRIMARY KEY.

2

Add the name column with NOT NULL constraint

Modify the employees table creation statement to add a name column of type TEXT that has a NOT NULL constraint.

SQL

CREATE TABLE employees (
    id INTEGER PRIMARY KEY,
    -- Add name column with NOT NULL constraint below
    
);

Need a hint?

Add name TEXT NOT NULL as a column definition.

3

Insert a valid employee record

Write a SQL statement to insert a new employee with id 1 and name 'Alice' into the employees table.

SQL

-- Insert an employee with id 1 and name 'Alice'
-- Your code here

Need a hint?

Use INSERT INTO employees (id, name) VALUES (1, 'Alice').

4

Try inserting a record with NULL name (should fail)

Write a SQL statement to insert a new employee with id 2 and name as NULL into the employees table. This should fail because of the NOT NULL constraint.

SQL

-- Insert an employee with id 2 and name NULL
-- Your code here

Need a hint?

Use INSERT INTO employees (id, name) VALUES (2, NULL) to see the NOT NULL constraint in action.