PostgreSQL vs MySQL vs SQL Server: Which Database Should You Choose?

The Big Three: An Overview

PostgreSQL, MySQL, and SQL Server are widely used relational database systems with mature ecosystems. Yet they differ in philosophy, licensing, syntax, and feature depth — so the "best" choice depends on your project's needs.

PostgreSQL

An open-source, object-relational database known for standards compliance and extensibility. PostgreSQL supports advanced types (JSONB, arrays, hstore), full-text search, CTEs, window functions, and custom extensions like PostGIS. Its extensibility is useful when a project needs specialized types or extensions.

MySQL

An open-source relational database commonly used in web applications and the LAMP stack. Its InnoDB engine provides ACID transactions, and recent versions have closed the feature gap with PostgreSQL significantly.

SQL Server

Microsoft's flagship RDBMS. SQL Server offers tight integration with the .NET ecosystem, database tooling such as SQL Server Management Studio and the MSSQL extension for Visual Studio Code, built-in business-intelligence features, and enterprise support. The free Express edition has version-specific resource limits. Developer editions are for development and testing, not production use.

Syntax Differences at a Glance

While all three speak SQL, day-to-day syntax varies enough to trip up developers switching between engines. Here are the most common differences:

Auto-Incrementing Primary Keys

-- PostgreSQL
CREATE TABLE users (
    id SERIAL PRIMARY KEY        -- or GENERATED ALWAYS AS IDENTITY
);

-- MySQL
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY
);

-- SQL Server
CREATE TABLE users (
    id INT IDENTITY(1,1) PRIMARY KEY
);

Identifier Quoting

-- PostgreSQL  →  double quotes
SELECT "order" FROM "user";

-- MySQL       →  backticks
SELECT `order` FROM `user`;

-- SQL Server  →  square brackets (or double quotes with QUOTED_IDENTIFIER ON)
SELECT [order] FROM [user];

String Concatenation

-- PostgreSQL
SELECT first_name || ' ' || last_name AS full_name FROM users;

-- MySQL
SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM users;

-- SQL Server
SELECT first_name + ' ' + last_name AS full_name FROM users;
-- or CONCAT() in SQL Server 2012+

Limiting Results

-- PostgreSQL & MySQL
SELECT * FROM products ORDER BY price LIMIT 10 OFFSET 20;

-- SQL Server (2012+)
SELECT * FROM products ORDER BY price
OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY;

Feature Comparison

Performance Characteristics

Performance depends on the workload, data distribution, version, configuration, and hardware. Compare representative queries and operational requirements instead of choosing an engine from a generic speed ranking:

• PostgreSQL: evaluate query plans, statistics, concurrency, and any extensions your workload requires.
• MySQL: evaluate the InnoDB configuration, indexes, isolation behavior, and execution plans for your actual application queries.
• SQL Server: evaluate rowstore or columnstore access paths, query plans, and the features available in your chosen edition.

In practice, the biggest performance gains come from proper indexing, query tuning, and schema design — not from switching engines. Visualise your schema in the Erd Go editor to spot relationship and indexing issues early.

Licensing & Cost

Compare total cost: licenses, hosting, backups, support, and the team’s operational experience. Consult each vendor’s current licensing terms before selecting an edition or redistributing software.

When to Pick Each Database

• Choose PostgreSQL when you need advanced data types, complex queries, spatial data (PostGIS), strong standards compliance, or its ecosystem and deployment options fit your project.
• Choose MySQL when your hosting provider already supports it, you rely on the LAMP/LEMP stack, or your team has deep MySQL expertise.
• Choose SQL Server when your stack is .NET / C#, you need tight Azure integration, your organisation already has Microsoft licensing, or you require built-in BI and reporting.

Regardless of which engine you choose, a clear schema design is critical. Use the Erd Go editor to map out your tables, relationships, and constraints visually — then test the schema and migrations in your target database.

References and further reading

• PostgreSQL: defining tables and database objects
• MySQL 8.4 reference manual
• Microsoft: SQL Server 2025 editions and limits
• Microsoft: native JSON type and version availability