The UNION operator can be used to combine the result-set of two or more SELECT statements. However this approach works only if your data set is derived from a single relational data. BIRT gives you the flexibility to pull in data from multiple sources that may or may not support SQL statements to perform a union. <br />
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With a little bit of scripting you could create a merged data set that would represent a union of multiple data sets. The approach involves creating a scripted data source - data set and constructing a global array(or any other temporary location) to hold the required data set values during the "onFetch" event of each data set and using this array to provide for the merged results in "fetch" event of the scripted data set. <br />
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The attached example is using such approach to merge "Data Set1", "Data Set2", "Data Set3" as a single "Union Data Set". It also has three tables (invisible) that has binding to the three data sets. This is done in order to ensure that each data set used for merging is executed. <br />
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See Live Report<br />
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Ashwini Verma
