This page is a quick reference checkpoint for AVG OVER in SQL Server: behavior, syntax rules, edge cases, and a minimal example; plus the official vendor documentation.
AVG OVER returns the average value of an expression across the window frame.
AVG divides the sum of non-null values by the count of non-null values; when used with OVER and ORDER BY it becomes nondeterministic.
If this behavior feels unintuitive, the tutorial below explains the underlying pattern step-by-step.
AVG supports [ ALL | DISTINCT ] and the OVER clause with optional PARTITION BY and ORDER BY.
SELECT AVG(SalesAmount) OVER (PARTITION BY Region ORDER BY OrderDate) AS AvgSalesByRegionOverTime 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.
AVG OVER is part of a bigger window-function pattern. If you want the “why”, start here: Aggregate Window Functions
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 SQL Server Documentation →Looking for more functions across all SQL dialects? Visit the full SQL Dialects & Window Functions Documentation.