Creating Auto-Incrementing Columns in SQL

Query Uses SEQUENCE in PostgreSQL and IDENTITY in SQL Server

Write a SQL query to create an auto-incrementing column, using SEQUENCE in PostgreSQL and IDENTITY in SQL Server.

Solution:

-- PostgreSQL
CREATE SEQUENCE EmployeeIDSeq START WITH 1 INCREMENT BY 1;

CREATE TABLE Employees (
    EmployeeID INT DEFAULT NEXTVAL('EmployeeIDSeq'),
    Name VARCHAR(100)
);

-- SQL Server
CREATE TABLE Employees (
    EmployeeID INT IDENTITY(1,1),
    Name VARCHAR(100)
);

Explanation:

• Purpose of the Query :
• The goal is to demonstrate how auto-incrementing columns are implemented differently in PostgreSQL and SQL Server.
• Key Components :
• SEQUENCE (PostgreSQL): Defines a sequence for generating unique values.
• IDENTITY (SQL Server): Automatically increments column values.
• Why Compare Auto-Incrementing Columns?:
• Understanding these differences ensures correct schema design across platforms.
• It simplifies migration and integration efforts.
• Real-World Application :
• In transactional systems, auto-incrementing columns simplify primary key generation.

Additional Notes:

• Use SEQUENCE in PostgreSQL for flexibility and IDENTITY in SQL Server for simplicity.
• Test queries on all target platforms to ensure consistent results.
• Important Considerations:
• Handle sequence resets or identity reseeds carefully during migrations.

For more Practice: Solve these Related Problems:

• Write a SQL query to create an auto-incrementing column for product IDs, using SEQUENCE in PostgreSQL and IDENTITY in SQL Server.
• Write a SQL query to create an auto-incrementing column for order IDs, using SEQUENCE in PostgreSQL and IDENTITY in SQL Server.
• Write a SQL query to create an auto-incrementing column for customer IDs, using SEQUENCE in PostgreSQL and IDENTITY in SQL Server.
• Write a SQL query to create an auto-incrementing column for employee IDs, using SEQUENCE in PostgreSQL and IDENTITY in SQL Server.

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous SQL Exercise:Writing a Using ILIKE in PostgreSQL and LIKE in MySQL/SQL Server.
Next SQL Exercise: Using ARRAY Data Types in PostgreSQL and JSON in MySQL.