As per conversion titled "entity-engine union support" (http://n4.nabble.com/entity-engine-union-support-td1607240.html#a1607240); here is the basic union support that we had added into our Ofbiz project. I have changed a little of the xml schema here ... the premise is that a "UnionViewEntity" extends the standard "ViewEntity" and contains a list of union members that it will union together. There should only be changes to the ModelReader to instantiate the new model object and then in SqlJdbcUtil to handle generating the new sql for unions. I have included a very small unit test that executes a findList against a test union.
Here is sample sql that was generated:
SELECT uva.UNION_ID, uva.TESTING_NAME, uva.TESTING_SIZE, uva.TESTING_DATE FROM ( SELECT T1.TESTING_ID AS UNION_ID, T1.TESTING_NAME AS TESTING_NAME, T1.TESTING_SIZE AS TESTING_SIZE, T1.TESTING_DATE AS TESTING_DATE FROM TESTING T1 UNION SELECT T2.TESTING_TYPE_ID AS UNION_ID, T2.TESTING_NAME AS TESTING_NAME, T2.TESTING_SIZE AS TESTING_SIZE, T2.TESTING_DATE AS TESTING_DATE FROM TESTING T2 ) uva