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Tuple Expressions

This section describes how to create and use tuple expressions in DeepSee MDX.

Details

In DeepSee MDX, a tuple expression can have either of the following forms:

  • A tuple literal, which is a comma-separated list of member expressions, enclosed by parentheses:

    (member_expr1, member_expr2, member_expr3, ...)
    

    Where member_expr1, member_expr2, member_expr3, and so on are member expressions. The parentheses are required.

  • A reference to a pivot variable that contains a tuple literal. To refer to a pivot variable, use the following syntax:

    $VARIABLE.variablename
    

    Where variablename is the logical variable name. Do not enclose this expression with square brackets. This syntax is not case-sensitive; nor is the pivot variable name.

    For information on defining pivot variables, see “Defining and Using Pivot Variables” in Using the DeepSee Analyzer.

Notes and Additional Terminology

In other implementations of MDX, a tuple cannot include more than one member from the same dimension. In DeepSee MDX, a tuple expression can include more than one member expression from the same dimension. In most cases, the result is null. However, in DeepSee, a level can be based on a list value, which means that a given record can belong to multiple members. For example, the tuple (allerd.soy,allerd.wheat) represents all patients who are allergic to both soy and wheat, and this tuple could potentially have a non-null value.

If the tuple refers to each dimension in the cube, the tuple is fully qualified. Otherwise, it is partially qualified. The following shows an example of a partially qualified tuple from the Patients cube:

(allerd.[dairy products], colord.red, aged.35)
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Another partially qualified tuple is as follows:

(diagd.asthma, aged.[age group].[30 to 59], MEASURES.[%COUNT])
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Also, note that each data cell returned by a query is a tuple.

The CROSSJOIN function returns a set of tuples, as does the NONEMPTYCROSSJOIN function.

Uses

You can use tuple expressions in the following ways:

  • As an element of a set.

  • As the argument to the WHERE clause.