A Window Function performs calculations across multiple rows while keeping the individual row data visible. Unlike GROUP BY, it does not merge rows into a single result but applies numeric calculations within a defined window(a subset of rows).
Note: It is used for aggregation (SUM, AVG), ranking (RANK, ROW_NUMBER), and offset calculations (LAG, LEAD) while maintaining row-wise output.
Syntax:
SELECT column_name,
AGGREGATE_FUNCTION(column_name) OVER (
PARTITION BY column_name
ORDER BY column_name
ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
) AS alias_name
FROM table_name;