AUTO_INCREMENT vs SERIAL vs IDENTITY in SQL - Hands-On Comparison

Understanding AUTO_INCREMENT, SERIAL, and IDENTITY in SQL

📖 Scenario: You are creating a simple database table to store user information for a website. Each user needs a unique ID that automatically increases as new users are added.

🎯 Goal: Build three versions of a user table using AUTO_INCREMENT, SERIAL, and IDENTITY to understand how each method creates an auto-incrementing primary key.

📋 What You'll Learn

Create a table named users_auto_increment using AUTO_INCREMENT for the ID column.

Create a table named users_serial using SERIAL for the ID column.

Create a table named users_identity using IDENTITY for the ID column.

💡 Why This Matters

🌍 Real World

Auto-incrementing IDs are used in real databases to uniquely identify records without manual input, making data management easier and more reliable.

💼 Career

Understanding these auto-increment methods is essential for database developers and administrators to design efficient and consistent database schemas.

1

Create a table with AUTO_INCREMENT

Write a SQL statement to create a table called users_auto_increment with two columns: id as an integer primary key that uses AUTO_INCREMENT, and username as a variable character string of length 50.

SQL

-- Your SQL code here to create users_auto_increment table with AUTO_INCREMENT

Need a hint?

Use AUTO_INCREMENT after the id column type to make it auto-increment in MySQL.

2

Create a table with SERIAL

Write a SQL statement to create a table called users_serial with two columns: id as a SERIAL primary key, and username as a variable character string of length 50.

SQL

-- Your SQL code here to create users_serial table with SERIAL

Need a hint?

Use SERIAL as the type for the id column in PostgreSQL to auto-increment.

3

Create a table with IDENTITY

Write a SQL statement to create a table called users_identity with two columns: id as an integer primary key using IDENTITY(1,1), and username as a variable character string of length 50.

SQL

-- Your SQL code here to create users_identity table with IDENTITY

Need a hint?

Use IDENTITY(1,1) for the id column in SQL Server to auto-increment.

4

Add a sample insert for each table

Write three SQL insert statements to add a user with username 'alice' into each table: users_auto_increment, users_serial, and users_identity. Do not specify the id value; let it auto-increment.

SQL

-- Your SQL code here to insert 'alice' into each table without specifying id

Need a hint?

Insert only the username column; the id will auto-increment automatically.