Calculates the cumulative distribution of a value in a group of values.
CUME_DIST is similar to PERCENT_RANK. Unlike PERCENT_RANK, which considers the RANK value in the presence of ties, CUME_DIST uses the highest tied rank, that is, the position of the last tied value when there are peers. CUME_DIST is the ratio of that position in the partition (RANK-HIGH/NUM ROWS).
ANSI SQL:2011 window function.