Exists (DMX)
Returns true if the specified sub-query returns at least one row.
Syntax
EXISTS(<subquery>)
Arguments
- subquery
A SELECT statement of the form SELECT * FROM <column name> [WHERE <predicate list>].
Result Type
Returns true if the result set returned by the subquery contains at least one row; otherwise, returns false.
Remarks
You can use the NOT keyword before EXISTS: for example, WHERE NOT EXISTS (<subquery>).
The list of columns that you add to the sub-query argument of EXISTS is irrelevant; the function only checks for the existence of a row that meets the condition.
Examples
You can use EXISTS and NOT EXISTS to check for conditions in a nested table. This is useful when creating a filter that controls the data used to train or test a data mining model. For more information, see Filters for Mining Models (Analysis Services - Data Mining).
The following example is based on the [Association] mining structure and mining model that you created in the Basic Data Mining Tutorial. The query returns only those cases where the customer purchased at least one patch kit.
SELECT * FROM [Association].CASES
WHERE EXISTS
(
SELECT * FROM [v Assoc Seq Line Numbers]
WHERE [[Model] = 'Patch kit'
)
Another way to view the same data that is returned by this query is to open the model in the Association viewer, right-click the itemset Patch kit = Existing, select the Drill Through option, and then select Model Cases Only.
See Also
Reference
Concepts
Model Filter Syntax and Examples (Analysis Services - Data Mining)