SQL Dialects (MySQL vs PostgreSQL)
SQL has a standard (ANSI/ISO SQL) but every database adds its own extensions and syntax variations. Understanding the key differences between MySQL and PostgreSQL saves hours of debugging when switching databases or working across teams using different systems.
Key Dialect Differences
- String concatenation: CONCAT() (MySQL) vs || operator (PostgreSQL)
- Auto-increment: AUTO_INCREMENT (MySQL) vs SERIAL/IDENTITY (PostgreSQL)
- Date truncation: DATE_FORMAT() (MySQL) vs TO_CHAR() + DATE_TRUNC() (PostgreSQL)
- ILIKE case-insensitive LIKE: PostgreSQL only (MySQL LIKE is case-insensitive by default)
- FULL OUTER JOIN: supported in PostgreSQL, not MySQL
- JSON: both support JSON but syntax differs (MySQL JSON vs PostgreSQL JSONB)
- Transactional DDL: PostgreSQL only (MySQL DDL auto-commits)
- ON CONFLICT (PostgreSQL) vs ON DUPLICATE KEY UPDATE (MySQL)
MySQL vs PostgreSQL Side by Side
-- Auto-increment ID:
-- MySQL:
CREATE TABLE users (id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(100));
-- PostgreSQL:
CREATE TABLE users (id SERIAL PRIMARY KEY, name VARCHAR(100));
-- PostgreSQL modern:
CREATE TABLE users (id INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY, name VARCHAR(100));
-- String concatenation:
-- MySQL: CONCAT(a, ' ', b)
SELECT CONCAT(name, ' <', email, '>') AS contact FROM users;
-- PostgreSQL: || operator
SELECT name || ' <' || email || '>' AS contact FROM users;
-- Date formatting:
-- MySQL:
SELECT DATE_FORMAT(created_at, '%Y-%m-%d') FROM orders;
-- PostgreSQL:
SELECT TO_CHAR(created_at, 'YYYY-MM-DD') FROM orders;
-- Current timestamp:
-- MySQL: NOW() or CURRENT_TIMESTAMP (same)
-- PostgreSQL: NOW() or CURRENT_TIMESTAMP or LOCALTIMESTAMP
-- Upsert (INSERT or UPDATE):
-- MySQL:
INSERT INTO users (id, name, email) VALUES (1, 'John', 'john@.com')
ON DUPLICATE KEY UPDATE name = VALUES(name), email = VALUES(email);
-- PostgreSQL:
INSERT INTO users (id, name, email) VALUES (1, 'John', 'john@.com')
ON CONFLICT (id) DO UPDATE SET name = EXCLUDED.name, email = EXCLUDED.email;
-- Case-insensitive search:
-- MySQL: LIKE is case-insensitive by default (collation UTF8_general_ci)
SELECT * FROM products WHERE name LIKE '%phone%';
-- PostgreSQL: use ILIKE for case-insensitive
SELECT * FROM products WHERE name ILIKE '%phone%';Quick Quiz
Tip
Tip
Practice SQL Dialects MySQL vs PostgreSQL in small, isolated examples before integrating into larger projects. Breaking concepts into small experiments builds genuine understanding faster than reading alone.
JOINs combine rows from two tables based on related columns
Common Mistake
Warning
A common mistake with SQL Dialects MySQL vs PostgreSQL is skipping edge case testing - empty inputs, null values, and unexpected data types. Always validate boundary conditions to write robust, production-ready sql code.
Practice Task
Note
Practice Task - (1) Write a working example of SQL Dialects MySQL vs PostgreSQL from scratch without looking at notes. (2) Modify it to handle an edge case (empty input, null value, or error state). (3) Share your solution in the Priygop community for feedback.
Key Takeaways
- SQL has a standard (ANSI/ISO SQL) but every database adds its own extensions and syntax variations.
- String concatenation: CONCAT() (MySQL) vs || operator (PostgreSQL)
- Auto-increment: AUTO_INCREMENT (MySQL) vs SERIAL/IDENTITY (PostgreSQL)
- Date truncation: DATE_FORMAT() (MySQL) vs TO_CHAR() + DATE_TRUNC() (PostgreSQL)