# Explain Aggregate function and Roll up aggregate funtion in cognos?

#### Prakatta Profile Answers by Prakatta

• Mar 21st, 2013

Aggregate Function specifies what type of aggregation to be applied on a data item like Total ,Average, Min etc.,

The roll-up aggregation of any item is important only when you create the aggregation of Aggregate type. Otherwise leave it as automatic.

Best Example here

The Aggregate Function is used to rollup the values when "Auto Group & Summarize" is set to yes for the query, it applies some logic depending on the datatype. The Rollup Aggregate Function is used for summary values like totals in the report

For example:

Fred \$5
Fred \$15
Barney \$20
Barney \$30

Put both columns on your report,
Aggregate function tells Cognos what to do with them with each other, ie.if you specify Total, this will show...

Aggragate function-Total
Fred \$20
Barney \$50

Aggragate fuction-Average
Fred \$10
Barney \$25

Rollup Aggragate Function tells Cognos what to do when you want a "Rollup" at the end of the Report or a Grouping (usually a Total or Subtotal, but could be any of the functions.)
So, if Aggregate is set to Total and Rollup is set to Total you get this...
Fred \$20
Barney \$50
Summary \$70

If Aggregate is set to Total and Rollup is set to Average you get this...
Fred \$20
Barney \$50
Smmary \$35

#### Sandy

• Sep 24th, 2013

Different aggregate functions are used to perform different operations on the column of the table. Aggregate functions are MAX,MIN,SUM,AVG and COUNT. It makes the calculation more easier.