This page is a quick reference checkpoint for LAG in Redshift: behavior, syntax rules, edge cases, and a minimal example; plus the official vendor documentation.
LAG lets you look back at a previous row's value within the same partition.
No behavioral details such as default frames, NULL-handling, or ordering rules are described.
If this behavior feels unintuitive, the tutorial below explains the underlying pattern step-by-step.
Syntax supports LAG(value_expr[, offset[, default]]) OVER (window); offset and default are optional.
SELECT LAG(saletime, 1) OVER (PARTITION BY seller ORDER BY saletime) AS prev_sale FROM sales;
If you came here to confirm syntax, you’re done. If you came here to get better at window functions, choose your next step.
LAG is part of a bigger window-function pattern. If you want the “why”, start here: Lead Lag
Reading docs is useful. Writing the query correctly under pressure is the skill.
For the authoritative spec, use the vendor docs. This page is the fast “sanity check”.
View Redshift Documentation →Looking for more functions across all SQL dialects? Visit the full SQL Dialects & Window Functions Documentation.