This page is a quick reference checkpoint for CUME_DIST in IBM DB2: behavior, syntax rules, edge cases, and a minimal example; plus the official vendor documentation.
CUME_DIST returns the cumulative distribution, showing the proportion of rows with values less than or equal to the current row.
Returns the cumulative distribution of the current row within its partition as a decimal between 0 and 1; first row receives a value > 0 depending on duplicates; single-row partitions return 1.
If this behavior feels unintuitive, the tutorial below explains the underlying pattern step-by-step.
Requires ORDER BY in the OLAP specification; computes number_of_rows_with_value_<=_current / rows_in_partition.
SELECT CUME_DIST() OVER (PARTITION BY dept ORDER BY salary) AS cume_dist 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.
CUME_DIST is part of a bigger window-function pattern. If you want the “why”, start here: Percentile Distribution
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 IBM DB2 Documentation →Looking for more functions across all SQL dialects? Visit the full SQL Dialects & Window Functions Documentation.