A window function that assigns a unique sequential integer to each row within the same window frame, starting with one.
ROW_NUMBER assigns a unique sequential integer to each row, starting with one. If multiple rows contain the same value for the window function field, each row is assigned a unique sequential integer.
The following example assigns numbers in sequential order to each employee (within each department) based on their salary:
SELECT ROW_NUMBER() OVER (PARTITION BY Department ORDER BY Salary) FROM Company.Employee