NOT NULL
- SQL course
- Beginner
- Lesson 91/115
- 4 min
Mark required columns with NOT NULL.
NOT NULL
With NOT NULL you mark a column as required. It is used for mandatory fields.
CREATE TABLE products (
id INT PRIMARY KEY,
name VARCHAR(100) NOT NULL
);Name cannot be null.
The table products is created.
NOT NULL — details
NOT NULL prevents inserting NULL into a column. It matters for data integrity; critical fields should always be NOT NULL.
Practice NOT NULL
Create products with id INT PRIMARY KEY and name VARCHAR(100) NOT NULL.
Starter code
-- create table
CREATE TABLE productsSample solution
CREATE TABLE products (
id INT PRIMARY KEY,
name VARCHAR(100) NOT NULL
)Expected output
Tablo oluşturuldu
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 NOT NULL: match the terms
| Term | Meaning |
|---|---|
NOT NULL |
not null |
PRIMARY KEY |
primary |
UNIQUE |
unique |
DEFAULT |
default |
2 Required field
Question
CREATE TABLE products (
id INT PRIMARY KEY,
name VARCHAR(100) ____
);
Answer
CREATE TABLE products (
id INT PRIMARY KEY,
name VARCHAR(100) NOT NULL
);Explanation: NOT NULL is the right answer.
3 What does NOT NULL prevent?
- Unique values
- Inserting empty (NULL) values Correct answer
- Deletes
- Updates
Explanation: NOT NULL prevents NULL input.