This page is a quick reference checkpoint for COUNT OVER in SQL Server: behavior, syntax rules, edge cases, and a minimal example; plus the official vendor documentation.
COUNT OVER returns the number of rows in the window frame.
When used with OVER, COUNT returns the count of rows in the window; may include or exclude NULL depending on COUNT vs COUNT(column).
If this behavior feels unintuitive, the tutorial below explains the underlying pattern step-by-step.
COUNT supports the OVER clause, with optional PARTITION BY and ORDER BY.
SELECT COUNT() OVER (PARTITION BY Department ORDER BY HireDate) AS RunningCount 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.
COUNT 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.