This page is a quick reference checkpoint for COUNT OVER in BigQuery: 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 an aggregate function is used with OVER, it becomes a window function. Aggregate-function clauses such as DISTINCT cannot be used together with OVER.
If this behavior feels unintuitive, the tutorial below explains the underlying pattern step-by-step.
COUNT([ DISTINCT ] expression) [ OVER (window_clause) ]
SELECT region, amount, COUNT(*) OVER (PARTITION BY region) AS region_count FROM sales_table;
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 BigQuery Documentation →Looking for more functions across all SQL dialects? Visit the full SQL Dialects & Window Functions Documentation.