The Union function joins two input sets, optionally retaining duplicates. Syntax:
Union (set, set [,ALL])
Use the Union function to lump two sets together into one set.
Results: A comparison of theses query results with the results using the Intersect function (see Exercise: Using the Intersect Function) shows that while Intersect returns a set containing only those children of East that have a UDA of “Major Market,” Union returns {all children of east) + (all Market Members that have a UDA of “Major Market”).
For more examples using pure set-operative functions, see the Oracle Essbase Technical Reference.