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SQLWindow Function
By Sitraka Forler · Lecturer, Durham Business SchoolUpdated 13 September 2026 About this site
Performs a calculation across rows related to the current row.
Window functions (OVER clause) do not collapse rows like GROUP BY. They add a computed column alongside existing data. Key functions: ROW_NUMBER, RANK, SUM, AVG, LAG, LEAD.
Example
AVG(close) OVER (PARTITION BY ticker ORDER BY date ROWS BETWEEN 19 PRECEDING AND CURRENT ROW)