CUME_DIST aggregate function
The CUME_DIST function returns the cumulative distribution of a row that is hypothetically inserted into a group of rows.
The schema is SYSIBM.
 expression
 An expression that specifies a row that is hypothetically inserted into a group of rows. The expression must return a value that is a builtin data type. The expression must be a constant, a variable, or a cast of a constant or variable (SQLSTATE 428I9).
 WITHIN GROUP
 Indicates that the aggregation follows the specified ordering within the grouping set.
 orderbyclause

 ORDER BY
 Specifies the order of the rows from the same grouping set that are processed in the aggregation.
 sortkey
 The sort key can be a column name or a sortkeyexpression. If the sort key is a constant, it does not refer to the position of the output column (as in the ordinary ORDER BY clause), but it is a constant, which implies no sort key.
 ASC
 Uses the values of the sortkey in ascending order.
 DESC
 Uses the values of the sortkey in descending order.
 NULLS FIRST
 The ordering considers null values before all nonnull values in the sort order.
 NULLS LAST
 The ordering considers null values after all nonnull values in the sort order.
The number of expressions must be the same as the number of sortkey expressions (SQLSTATE 42822). The data type of each expression and the data type of the corresponding sortkey expression must be compatible (SQLSTATE 42822).
The data type of the result is DECFLOAT(34). The actual result is greater than 0.0 and less than or equal to 1.0.
Example
Set the host variable CD to the cumulative distribution of a hypothetical new employee's salary
of 47000 within the salaries of the employees in department
'A00'.
SELECT CUME_DIST(47000) WITHIN GROUP (ORDER BY SALARY)
INTO :CD FROM EMPLOYEE WHERE WORKDEPT = 'A00'