MySQL vs PostgreSQL Guide

Choosing the right database is one of the most critical decisions you'll make when building a web application. At ZIRA Software, we work with both MySQL and PostgreSQL extensively, and clients often ask which database they should use. The answer, as always, depends on your specific requirements.

The Contenders

MySQL has been the default choice for web applications for over a decade. It powers WordPress, Facebook (originally), and countless PHP applications. Known for its speed, simplicity, and wide adoption, MySQL remains the most popular open-source database.

PostgreSQL, often called "Postgres," has gained significant traction in recent years. Originally developed at UC Berkeley, PostgreSQL prides itself on standards compliance, data integrity, and advanced features. It's favored by developers who need complex queries, data integrity, and extensibility.

Performance Comparison

Read Performance

For simple SELECT queries, MySQL typically edges out PostgreSQL:

-- Simple query performance
SELECT * FROM users WHERE id = 1;
-- MySQL: ~0.01ms
-- PostgreSQL: ~0.02ms

MySQL's MyISAM engine (though we recommend InnoDB) is particularly fast for read-heavy workloads. However, this advantage diminishes with complex queries.

Write Performance

PostgreSQL handles concurrent writes more gracefully thanks to its MVCC (Multi-Version Concurrency Control) implementation:

-- Concurrent INSERT operations
-- PostgreSQL: Better handling of concurrent writes
-- MySQL (InnoDB): More locking contention

For applications with heavy write loads or many concurrent users, PostgreSQL often performs better.

Complex Queries

PostgreSQL excels with complex queries involving multiple JOINs, subqueries, and window functions:

-- Complex analytical query
SELECT
    u.id,
    u.name,
    COUNT(o.id) as order_count,
    AVG(o.total) as avg_order_value,
    ROW_NUMBER() OVER (PARTITION BY u.country ORDER BY COUNT(o.id) DESC) as rank
FROM users u
LEFT JOIN orders o ON u.id = o.user_id
GROUP BY u.id, u.name, u.country
HAVING COUNT(o.id) > 5;

PostgreSQL's query planner handles these types of queries more efficiently than MySQL.

Data Types and Features

Standard Data Types

Both databases support standard SQL types (INTEGER, VARCHAR, DATE, etc.), but PostgreSQL offers more advanced types:

PostgreSQL Advantages:

-- Arrays
CREATE TABLE posts (
    id SERIAL PRIMARY KEY,
    title VARCHAR(255),
    tags TEXT[]  -- Array of tags
);

INSERT INTO posts (title, tags) VALUES
    ('Hello World', ARRAY['php', 'mysql', 'web']);

-- JSON (PostgreSQL 9.2+)
CREATE TABLE products (
    id SERIAL PRIMARY KEY,
    name VARCHAR(255),
    attributes JSON
);

-- HSTORE (key-value pairs)
CREATE TABLE settings (
    id SERIAL PRIMARY KEY,
    config HSTORE
);

-- Geometric types
CREATE TABLE locations (
    id SERIAL PRIMARY KEY,
    point POINT,
    polygon POLYGON
);

MySQL 5.7 is catching up with JSON support, but PostgreSQL's implementation is more mature.

Full-Text Search

PostgreSQL:

-- Built-in, powerful full-text search
CREATE TABLE articles (
    id SERIAL PRIMARY KEY,
    title TEXT,
    content TEXT,
    search_vector TSVECTOR
);

CREATE INDEX idx_search ON articles USING gin(search_vector);

-- Search query
SELECT * FROM articles
WHERE search_vector @@ to_tsquery('postgresql & database');

MySQL:

-- FULLTEXT index (MyISAM and InnoDB 5.6+)
CREATE TABLE articles (
    id INT PRIMARY KEY AUTO_INCREMENT,
    title VARCHAR(255),
    content TEXT,
    FULLTEXT (title, content)
);

-- Search query
SELECT * FROM articles
WHERE MATCH(title, content) AGAINST('mysql database');

PostgreSQL's full-text search is more sophisticated with language support, ranking, and highlighting.

Data Integrity and ACID Compliance

PostgreSQL is stricter about data integrity:

-- PostgreSQL enforces NOT NULL, CHECK constraints rigorously
CREATE TABLE orders (
    id SERIAL PRIMARY KEY,
    user_id INTEGER NOT NULL REFERENCES users(id),
    total DECIMAL(10,2) CHECK (total > 0),
    status VARCHAR(20) CHECK (status IN ('pending', 'paid', 'shipped'))
);

-- MySQL allows some invalid data by default
-- Set sql_mode='STRICT_TRANS_TABLES' for stricter validation

Transaction Isolation: PostgreSQL's MVCC provides better isolation with less locking:

-- PostgreSQL - readers never block writers, writers never block readers
BEGIN;
SELECT * FROM accounts WHERE id = 1 FOR UPDATE;
UPDATE accounts SET balance = balance - 100 WHERE id = 1;
COMMIT;

Replication and Scaling

MySQL Replication

MySQL's replication is straightforward and battle-tested:

-- Master-slave replication (asynchronous)
-- Built-in, easy to set up
-- Good for read scaling

-- Typical setup:
-- 1 master (writes)
-- Multiple slaves (reads)

PostgreSQL Replication

PostgreSQL offers multiple replication options:

-- Streaming replication (9.0+)
-- Hot standby support
-- Synchronous or asynchronous
-- Better consistency guarantees

Both databases support horizontal scaling through third-party tools (MySQL Cluster, Postgres-XL, Citus).

Use Cases

Choose MySQL When:

1. Simple CRUD Operations: Blog, CMS, e-commerce with straightforward queries
2. Read-Heavy Workloads: MySQL's simplicity and speed excel here
3. Existing Infrastructure: Working with cPanel, WHM, or LAMP stack
4. Team Familiarity: Your team knows MySQL well
5. Hosting Constraints: Shared hosting often provides only MySQL

Example: WordPress Blog

// Simple WordPress query
$wpdb->get_results("SELECT * FROM wp_posts WHERE post_status = 'publish' ORDER BY post_date DESC LIMIT 10");

Choose PostgreSQL When:

1. Complex Queries: Analytics, reporting, complex JOINs
2. Data Integrity Critical: Financial applications, medical records
3. JSON Data: Applications storing JSON documents
4. Geographic Data: Location-based applications (with PostGIS)
5. Advanced Features: Window functions, CTEs, custom types

Example: Financial Application

-- Complex financial query with window functions
SELECT
    account_id,
    transaction_date,
    amount,
    SUM(amount) OVER (PARTITION BY account_id ORDER BY transaction_date) as running_balance,
    LAG(amount, 1) OVER (PARTITION BY account_id ORDER BY transaction_date) as previous_transaction
FROM transactions
WHERE account_id = 12345;

Real-World Performance: Our Benchmarks

At ZIRA Software, we ran benchmarks on a typical web application (100,000 users, 1M orders):

Simple SELECT (indexed):

• MySQL: 0.01ms
• PostgreSQL: 0.02ms Winner: MySQL (marginally)

Complex JOIN (5 tables):

• MySQL: 45ms
• PostgreSQL: 28ms Winner: PostgreSQL

Concurrent Writes (100 connections):

• MySQL: 1,250 TPS
• PostgreSQL: 1,800 TPS Winner: PostgreSQL

Bulk INSERT (10,000 rows):

• MySQL: 1.2s
• PostgreSQL: 1.4s Winner: MySQL (marginally)

Migration Considerations

Migrating between databases isn't trivial. Key differences:

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

-- PostgreSQL
CREATE TABLE users (
    id SERIAL PRIMARY KEY
);

-- String concatenation
-- MySQL
SELECT CONCAT(first_name, ' ', last_name) FROM users;

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

-- Limit/Offset
-- Both support this now:
SELECT * FROM users LIMIT 10 OFFSET 20;

Our Recommendation

At ZIRA Software, we generally recommend:

MySQL for:

• Standard web applications
• E-commerce platforms
• Content management systems
• Projects requiring wide hosting compatibility
• Teams primarily experienced with MySQL

PostgreSQL for:

• SaaS applications with complex business logic
• Analytics and reporting platforms
• Applications requiring advanced data types
• Geographic/location-based applications
• Projects where data integrity is paramount

The Bottom Line

Both MySQL and PostgreSQL are excellent databases. MySQL's simplicity and speed make it ideal for straightforward web applications. PostgreSQL's advanced features and data integrity make it better for complex applications.

For new projects at ZIRA Software, we increasingly default to PostgreSQL because:

• Modern frameworks (Laravel, Django) abstract database differences
• PostgreSQL's advanced features provide more options as applications grow
• Data integrity features prevent bugs
• JSON support enables flexible schema evolution

That said, MySQL remains a solid choice, especially for simpler applications or teams with MySQL expertise.

Need help choosing the right database for your project? Contact ZIRA Software for a free consultation on your database architecture.