Limited Support for Relational Functions When Used with OLAP Data Sources
When working with an OLAP data source, we recommend
that you not use relational functions, such as
substring and
concatenation functions, in a report that also contains a measure
with the Aggregate Function property set to Calculated or Automatic in
the model. If you do so, you may encounter unexpected results. For
example, some summaries are calculated using the Minimum function
instead of the aggregate function derived from the individual query
items.
In the expression editor, an exclamation mark (!) that precedes a function indicates that the function is not naturally supported for that data source. IBM® Cognos® Analytics with Watson uses a local approximation for that function. Because an approximation is used, performance can be degraded and the results may not be what you expect.
For example, you create an IBM Cognos Query Studio report that contains the data items Product line and Retailer site count. The footer summary is set to Calculated. You then insert a calculated column that returns the first three characters of the Product line item, which uses the relational concatenation function. The footer summary now shows the lowest gross margin value.
