Aggregation

[cielo]

Can someone enlighten me the difference between Summary aggregation and Details aggregation. do we need to set both for each data item,when we set default Cognos will take care according to the DB data type/values? Please assist

[MFGF]

Can someone enlighten me the difference between Summary aggregation and Details aggregation. do we need to set both for each data item,when we set default Cognos will take care according to the DB data type/values? Please assist

Hi,

The first point to recognise is that Cognos will automatically group and aggregate detail rows from your database. For example, if you bring in a descriptive item, and a particular value for that item exists on 100 rows in your data source, you would see just that one value displayed in your report, rather than seeing it repeated 100 times. If you then added a measure to the report, you would see an aggregated value for the measure next to that one value. The type of aggregation used in this case is whatever is defined as the detail aggregation, eg if it was set to average you would see an average value of the measure from those 100 detail rows.

If you are using something like a list (or a crosstab) in your report, you will often want to add group summaries. For example, in a list you might have two descriptive items and a measure eg Country and City with Revenue. There would obviously be multiple rows displayed for the same country, because the country has multiple cities. You might decide to group the list on the Country item, then add group summaries for the measure, shown as aggregated values in the group footings. In this case you would first click on the Country column and press the Group button, then click on the Revenue column and press the Aggregate button. At this point you can choose how to aggregate explicitly for the footings (eg Total) or you can choose the Automatic aggregation option. If you choose this automatic option, then this is where whatever is defined as the summary aggregation is used.

Cheers!

MF.

[cielo]

Thank you for the detailed explanation.