This page is a quick reference checkpoint for LAG in ORACLE: 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.
Behavior: LAG returns value from a preceding row; if offset goes beyond the partition, default is returned (or NULL if omitted). Evaluated after windowing. ORDER BY defines row sequencing.
If this behavior feels unintuitive, the tutorial below explains the underlying pattern step-by-step.
Syntax: LAG(value_expr [, offset [, default ]]) OVER (analytic_clause). Offset and default are optional.
SELECT last_name, hire_date, salary, LAG(salary,1) OVER (ORDER BY hire_date) AS prev_sal FROM employees;
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 ORACLE Documentation →Looking for more functions across all SQL dialects? Visit the full SQL Dialects & Window Functions Documentation.