Data Mining Extensions - DMX - Reference

TOP and ORDER BY
You can order the results of a query by using an expression, and can then return a subset
of the results by using a combination of the ORDER BY and TOP clauses. This is useful in
a scenario such as targeted mailing where you only want to send results to the most
likely respondents. You could order the results of a target mailing prediction query by
the prediction probability, and then only return the top results.
Select List
The can include scalar column references, prediction functions, and
expressions. The options that are available depend on the algorithm, and the following
contexts:
• Whether you are querying a mining structure or a mining model
• Whether you are querying content or cases
• Whether source data is a relational table or a cube
• If you are making predictions
In many cases, you can use aliases, or create simple expressions based on the items in
the select list. For example, the following example shows a simple expression on model
columns:
SELECT [CustomerID], [Last Name] + ', ' + [FirstName] AS FullName
FROM .CASES
The following example creates an alias for a column that contains the results of a
prediction function:
SELECT Predict([Column1], 'Value') as Column1Prediction
FROM MyModel
JOIN
WHERE
You can limit the cases that are returned by the query by using a WHERE clause. The
WHERE clause specifies that column references in the WHERE expression must have the
same semantics as column references in the of the SELECT statement, and
can only return a Boolean expression. The syntax for the WHERE clause is as follows
WHERE < condition expression >
The select list and WHERE clause of a SELECT statement must follow the following rules:
• The select list must contain an expression that does not return a Boolean result. You
can modify the expression, but the expression must return non-Boolean results.
• The WHERE clause must contain an expression that returns a Boolean result. You can
modify the clause, but it must return a Boolean result.
Predictions
There are two types of syntax that you can use for creating predictions:
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