PostgreSQL LAG() Function

Syntax

LAG(column, offset) OVER (ORDER BY column)

Basic Example

SELECT name, salary,
       LAG(column, offset) OVER (ORDER BY column) AS result
FROM employees;

When to use it

Use LAG when you need a window operation in PostgreSQL. This page is designed as a quick reference for developers, analysts, and students comparing SQL dialects.

Common mistake

A common mistake is copying syntax from another SQL dialect. Always verify function name, argument order, and formatting tokens for PostgreSQL.

Related SQL Functions

• MySQL ROW_NUMBER() Function
• MySQL RANK() Function
• MySQL DENSE_RANK() Function
• MySQL LAG() Function
• MySQL LEAD() Function
• MySQL FIRST_VALUE() Function

FAQ

Is LAG available in every SQL database?

Not always. Function names and argument behavior can differ across SQL engines.

Can I use this in SELECT queries?

Yes. Most SQL functions are commonly used in SELECT and often in WHERE, ORDER BY, and GROUP BY depending on the function.