SQL · Functions and expressions

lag() / lead()

Reads the previous or next row in a window, useful for deltas.

sqlRunnable example sql course

Syntax

lag(column) over (…)

Example

Open in the lab

WITH lessons(minutes) AS (VALUES (10), (15), (30))
SELECT minutes, minutes - lag(minutes) OVER (ORDER BY minutes) AS change FROM lessons;

Reference pages are the quick answer. The course explains the why, shows the full example and ends with a challenge.