Count and IIF

Caveat: Note that IIF is not listed in the TM1 v9.0 SP2 help file as being supported so use at your own risk.

Count returns the number of items in a set but this set can be a set of members or a set of data values. The result is, obviously, a number and is often returned in reports when used in MDX queries outside of TM1. When trying to use it do define a TM1 subset it can only be used as part of the query logic and not as a result itself.

Count can be wrapped around a lot of the other MDX functions and so can be used in many different scenarios. One example is to count how many children a month has and, if there are 28, doing something that is unique to February. Although dimension subsets are usually a list of meaningful items in a business model and are included within application cubes, it is actually possible to have dimensions for administrator purposes only (that are never used to build cubes) which might indicate the state of something – e.g. “All Passwords Set”, or “Reconciliation Failed” and the Count function could be used to define a subset that contains one of these members, which is information for the administrator only.

IIF allows you to introduce some branching logic in your queries – i.e. do one thing if this is true, otherwise do something else. You could use it to apply different statistical functions to members that have certain attributes. It works quite commonly with Count to allow one thing to happen if the count of something falls below a threshold, or do something else if not.

This example performs either a Top 5 or a Top 10 on all base products’ Amounts in the Test cube, depending on whether the number of base level Products is 10 or less at the time the query is run.
{ TOPCOUNT( {TM1FILTERBYLEVEL( {TM1SUBSETALL( [Product] )}, 0)},
IIF(Count({TM1FILTERBYLEVEL( {TM1SUBSETALL( [Product] )}, 0)}) <= 10, 5, 10),
[Test].([Posting Measures].[Amount]) )}

This example does a TopCount of the base products based on their Amount value in the Test cube where the number of items displayed is equal to the number of cells in the Test cube whose Amount value is anything other than zero.
{TOPCOUNT(
    {TM1FILTERBYLEVEL( {TM1SUBSETALL( [Product] )}, 0)},
    Count(
        Filter({TM1FILTERBYLEVEL( {TM1SUBSETALL( [Product] )}, 0)}, [Test].([Posting Measures].[Amount]) <> 0),
         )
    )
}
These are fairly pointless examples, practically speaking, but they show the syntax.