Is PostgreSQL syntax compatible with MySQL?

Mostly, but not fully. Standard SELECT, JOIN, WHERE, GROUP BY, and common data types are the same. The breaking differences are auto-increment columns, identifier quoting, string concatenation, upsert syntax, and some function names. A query using only standard SQL usually ports cleanly; one using dialect shortcuts needs edits.

Why does || not work for string concatenation in MySQL?

By default MySQL treats || as the logical OR operator, so 'a' || 'b' evaluates as a boolean expression rather than concatenating. PostgreSQL follows the SQL standard where || concatenates strings. Use CONCAT() in MySQL, or enable the PIPES_AS_CONCAT SQL mode to make || concatenate.

What replaces AUTO_INCREMENT in PostgreSQL?

Use GENERATED ALWAYS AS IDENTITY, the SQL-standard syntax supported since PostgreSQL 10 and the recommended choice. The older SERIAL pseudo-type also works and creates an underlying sequence. Both give you an auto-incrementing integer primary key equivalent to MySQL's AUTO_INCREMENT.

How do I convert a MySQL upsert to PostgreSQL?

Replace INSERT ... ON DUPLICATE KEY UPDATE with INSERT ... ON CONFLICT (column) DO UPDATE SET. Where MySQL references the incoming row with VALUES(col), PostgreSQL uses EXCLUDED.col. You must name the conflicting unique or primary-key column in the ON CONFLICT clause, which MySQL infers automatically.

SQL Dialects

MySQL vs PostgreSQL: Key Syntax Differences

By Sharon Ben-Moshe · June 25, 2026 · 3 min read

Sharon Ben-Moshe is the founder of sqlfmt, a browser-based SQL formatter and validator with misspelled-keyword suggestions across PostgreSQL, MySQL, SQLite, SQL Server, and BigQuery.

The MySQL vs PostgreSQL syntax differences that break migrations: auto-increment, quoting, string concat, upserts, and NULL functions — with side-by-side SQL.

Quick answer

The main MySQL vs PostgreSQL syntax differences are: auto-increment (AUTO_INCREMENT vs GENERATED AS IDENTITY/SERIAL), identifier quoting (backticks vs double quotes), string concatenation (CONCAT() vs the || operator), and upserts (ON DUPLICATE KEY UPDATE vs ON CONFLICT). PostgreSQL follows the SQL standard more closely; MySQL has more permissive, non-standard shortcuts.

MySQL vs PostgreSQL: Key Syntax Differences

Quick answer

FAQs

Is PostgreSQL syntax compatible with MySQL?

Why does || not work for string concatenation in MySQL?

What replaces AUTO_INCREMENT in PostgreSQL?

How do I convert a MySQL upsert to PostgreSQL?

SQL COALESCE vs ISNULL: Key Differences

SQL ROW_NUMBER(): How to Number Rows

SQL Date Difference: DATEDIFF by Database

Auto-increment: AUTO_INCREMENT vs IDENTITY

Quoting identifiers: backticks vs double quotes

String concatenation: CONCAT() vs ||

Upserts: ON DUPLICATE KEY UPDATE vs ON CONFLICT

Functions and types that differ

Checklist: porting a query between MySQL and PostgreSQL

Wrapping up

Quick answer

FAQs

Is PostgreSQL syntax compatible with MySQL?

Why does || not work for string concatenation in MySQL?

What replaces AUTO_INCREMENT in PostgreSQL?

How do I convert a MySQL upsert to PostgreSQL?

Keep reading

SQL COALESCE vs ISNULL: Key Differences

SQL ROW_NUMBER(): How to Number Rows

SQL Date Difference: DATEDIFF by Database

Auto-increment: AUTO_INCREMENT vs IDENTITY

Quoting identifiers: backticks vs double quotes

String concatenation: CONCAT() vs ||

Upserts: ON DUPLICATE KEY UPDATE vs ON CONFLICT

Functions and types that differ

Checklist: porting a query between MySQL and PostgreSQL

Wrapping up