BottomCount (DMX)

THIS TOPIC APPLIES TO:yesSQL Server (starting with 2008)noAzure SQL DatabasenoAzure SQL Data Warehouse noParallel Data Warehouse

Returns the specified number of bottom-most rows, in increasing order of rank as specified by an expression.

Syntax


BottomCount(<table expression>, <rank expression>, <count>)  

Applies To

An expression that returns a table, such as a <table column reference>, or a function that returns a table.

Return Type

<table expression>

Remarks

The value that is supplied by the <rank expression> argument determines the increasing order of rank for the rows that are supplied in the <table expression> argument, and the number of bottom-most rows that is specified in the <count> argument is returned.

Examples

The following example creates a prediction query against the Association model that you build by using the Basic Data Mining Tutorial.

To understand how BottomCount works, it might be helpful to first execute a prediction query that returns only the nested table.

SELECT Predict ([Association].[v Assoc Seq Line Items], INCLUDE_STATISTICS, 10)  
FROM   
     [Association]  
NATURAL PREDICTION JOIN  
SELECT (SELECT 'Women''s Mountain Shorts' as [Model]) AS [v Assoc Seq Line Items]) AS t  

Note

In this example, the value supplied as input contains a single quotation mark, and therefore must be escaped by prefacing it with another single quotation mark. If you are not sure of the syntax for inserting an escape character, you can use the Prediction Query Builder to create the query. When you select the value from the dropdown list, the required escape character is inserted for you. For more information, see Create a Singleton Query in the Data Mining Designer.

Example results:

Model $SUPPORT $PROBABILITY $ADJUSTEDPROBABILITY
Sport-100 4334 0.291283016 0.252695851
Water Bottle 2866 0.192620472 0.175205052
Patch kit 2113 0.142012232 0.132389356
Mountain Tire Tube 1992 0.133879965 0.125304948
Mountain-200 1755 0.117951475 0.111260823
Road Tire Tube 1588 0.106727603 0.101229538
Cycling Cap 1473 0.098998589 0.094256014
Fender Set - Mountain 1415 0.095100477 0.090718432
Mountain Bottle Cage 1367 0.091874454 0.087780332
Road Bottle Cage 1195 0.080314537 0.077173962

The BottomCount function takes the results of this query and returns the smallest-valued rows that sum to the specified percentage.

SELECT   
BottomCount  
    (  
    Predict ([Association].[v Assoc Seq Line Items],INCLUDE_STATISTICS,10),  
    $SUPPORT,  
    3)  
FROM   
     [Association]  
NATURAL PREDICTION JOIN  
(SELECT (SELECT 'Women''s Mountain Shorts' as [Model]) AS [v Assoc Seq Line Items]) AS t  

The first argument to the BottomCount function is the name of a table column. In this example, the nested table is returned by calling the Predict function and using the INCLUDE_STATISTICS argument.

The second argument to the BottomCount function is the column in the nested table that you use to order the results. In this example, the INCLUDE_STATISTICS option returns the columns $SUPPORT, $PROBABILTY, and $ADJUSTED PROBABILITY. This example uses $SUPPORT because support values are not fractional and therefore are easier to verify.

The third argument to the BottomCount function specifies the number of rows. To get the three lowest-ranked rows, as ordered by $SUPPORT, you type 3.

Example results:

Model $SUPPORT $PROBABILITY $ADJUSTEDPROBABILITY
Road Bottle Cage 1195 0.080314537 0.077173962
Mountain Bottle Cage 1367 0.091874454 0.087780332
Fender Set - Mountain 1415 0.095100477 0.090718432

Note This example is provided only to illustrate the use of BottomCount. Depending on the size of your data set, this query might take a long time to run.

See Also

Functions (DMX)
General Prediction Functions (DMX)
BottomPercent (DMX)
BottomSum (DMX)
TopCount (DMX)