BEx Queries in SAP BW have a lot of logic and business rules, some reporting scenarios may require you to leverage your business rule of existing BEx queries and transform your BEx Queries to meet your requirement, for example the BEx queries has restricted and calculated key figures. Normally you must use APD ( Analysis Process Designer ) on existing BEx query or write ABAP Code in Transformation.
This example describes and feature in SAP BW 7.3 that allows you to use BEx Query as source for transformations, then you can transform the data and then save to an infoprovider.
1.Goto transaction RSA1, then select the Infoprovider that you want to save query result, right click and click CREATE TRANSFORMATION.
2.Select Query from the OBJECT TYPE dropdown, Input query name that you want to use as source, see picture below.
3.Map the appropriate fields in the transformation, you may also use transformation rules . After the transformation is created, then create the DTP and execute it to load data using BEx Query to the DSO.