Aggregating Data
One of the key features of any report is the ability to display summary, or aggregate, information. For example, a sales report can show the overall sales total; sales subtotals by product type, region, or sales representatives; average sales figures; or the highest and lowest sales figures.
Aggregating data involves performing a calculation on a set of values rather than on a single value. For a simple listing report, aggregate calculations are performed on values in a specific field, over all the data rows in the report.
BIRT calculates an average payment in a report by adding the values in the Amount field in every row, then dividing the total by the number of rows.
How to display aggregate data
1 On the palette, under Quick Tools, drag an aggregation element and drop it in the header or footer row of a group or a table.
1 In Column Binding Name, type a unique name. Remember, for each piece of calculated data to display in a report, there must be a column binding.
o If performing an aggregate calculation on values other than values in a data set field, type an expression. You can open the expression builder to get help constructing an expression.
5 In Filter Condition, specify the filter condition to use to determine which rows are factored in the aggregate calculation.
o Select a specific group to perform the aggregate calculation over all the rows in the selected group.Figure 9‑1 shows an example of a complete definition for an aggregation element. In the example, the element returns the number of rows in the table, where the extended price of the product is greater than $5,000.00.
Figure 9-1 Aggregation Builder displaying values for getting the count of products in the tableIn the report design, the aggregation element displays the sigma symbol followed by the column binding name, as shown in the following example:
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