PRIMARY KEY
- SQL course
- Beginner
- Lesson 93/115
- 4 min
Define a primary key.
AUTO_INCREMENT
With AUTO_INCREMENT (MySQL) a column auto-fills with an increasing number when omitted. PostgreSQL uses SERIAL.
CREATE TABLE products (
id INT AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(100)
);Id auto-increments; no manual value needed.
The table products is created.
AUTO_INCREMENT — details
PostgreSQL uses SERIAL or IDENTITY; SQL Server uses IDENTITY(1,1). An auto-increment column is usually the primary key.
Practice AUTO_INCREMENT
Create products with id INT AUTO_INCREMENT PRIMARY KEY and name VARCHAR(100).
Starter code
-- create table
CREATE TABLE productsSample solution
CREATE TABLE products (
id INT AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(100)
)Expected output
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Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Auto increment
Question
CREATE TABLE products (
id INT ____ PRIMARY KEY,
name VARCHAR(100)
);
Answer
CREATE TABLE products (
id INT AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(100)
);Explanation: AUTO_INCREMENT is the right answer.
2 PRIMARY KEY: match the terms
| Term | Meaning |
|---|---|
AUTO_INCREMENT |
auto increment |
SERIAL |
PostgreSQL |
PRIMARY KEY |
primary |
DEFAULT |
default |
3 What is used for auto-increment in PostgreSQL?
- SEQUENCE
- AUTO_INCREMENT
- IDENTITY
- SERIAL Correct answer
Explanation: PostgreSQL uses SERIAL.