About data sets

A data set is an object that defines all the data that is available to a report. To create a data set, you must have an existing BIRT data source. As with data sources, BIRT Report Designer provides wizards to create data sets. The first and the only required step in creating a data set is to select the data to retrieve from a data source. After this first step, you can optionally process the raw data as needed for the report. For example, you can change the names of columns, create computed columns, and define filters to provide a subset of the data to the report.

You can create as many data sets as are necessary for a report. Typically, you create at least one data set for each data source. For example, if you created a JDBC data source and an XML data source in a report, you would create a JDBC data set and an XML data set. You can also create multiple data sets that use a single data source. If, for example, a report displays sales data from the same database in a chart and in a table, you can create one data set to return data for the chart, and another data set to return data for the table. In this scenario, creating different data sets can improve performance because each data set retrieves only the specific data required by each report element. Alternatively, to use identical data, both items can share the same data set.

BIRT Report Designer provides a default name for each data set you create in a report. The names begin with Data Set. If you create two data sets, the default names are Data Set and Data Set1. You should use descriptive names, such as CorporateSalesDB or SupportLogXML, that enable you to identify easily the type of data that the data set provides.