Given a sort expression list, this Ordered Analytical function derives a new column indicating the rank of the rows when sorted by the specified sort expression list. When the column or expression has the same value for multiple rows (say M rows), they are all assigned the same rank, while the following M-1 rank values are not assigned. For example, column values 3,3,3,2,1 could be assigned rank values of 1,1,1,4,5. When one or more Partition Columns are specified, the ranks are determined separately over the rows in each partition (the ranking process is reset for each new partition). Rows options are not available with the Rank function.
A Teradata Warehouse Miner enhancement to the Rank function is offered to optionally request that NULL values in any element of the sort expression list cause the row to be excluded in the ranking process. Support is also provided for the WITH TIES option of the RANK function (provided the version of Teradata in use is 14.10 or later). The following table lists possible values for this option.
|With Ties Option||Description|
|(none)||When the WITH TIES option is not specified, the result is the same as if WITH TIES LOW was specified.|
|LOW||Equal values are given the same rank as the first value is given. This is the default behavior. For example, the values 10-10-10-20-30 are ranked 1-1-1-4-5, skipping ranks 2 and 3.|
|HIGH||Equal values are given the same rank as the last value would be given if each tie were given an incrementally increasing rank. For example, 10-10-10-20-30 are ranked 3-3-3-4-5, skipping 1,2.|
|AVG||Equal values are given the average of the ranks that would be given if each tie were given an incrementally increasing rank, returning a decimal rather than an integer value. For example, 10-10-10-20-30 are ranked 2.0-2.0-2.0-3.0-4.0 because 2.0 is the average of 1, 2 and 3.|
|DENSE||Equal values are given the same rank and the next value is given the next rank, so that ranks are not skipped. Using this option is equivalent to using the DENSE RANK function. For example, 10-10-10-20-30 are ranked 1-1-1-2-3.|
When dragging a Rank function into a variable, the following tree element is created.
Sort expressions can be built up in the Sort Expressions folder, Partition Columns can be built up in that folder. The WITH TIES option and the enhancement to the Rank function to optionally request that NULL values in any element of the sort expression list cause the row to be excluded in the ranking process is enabled through the Properties panel. Double-click on Rank, or highlight it and click Properties.