Union in CDS View with different columns

Question

Hello,
I have two entities E1 {a: Integer; b: Integer} and E2 {a: Integer; c: Integer} and I want to build a CDS view which does a union on both like:
SELECT a, b, null as c FROM E1
UNION SELECT a, null as b, c  FROM E2
I have written the following:
view UnionView as select from E1 {a, b, null as c} union select from E2 {a, null as b, c}
Now I get the error message: Feature is not supported
Has anybody an idea, how to model this with a CDS view? With a graphical calculation view, this is possible, but I want to build it as a CDS view.
Regards,
Michael

Answer 1

What revision is your system on?  I show that UNION was new syntax in SPS 09.
http://help.sap.com/hana/SAP_HANA_Core_Data_Services_CDS_Reference_en.pdf
I tried the following in my system and it worked just fine:
namespace playground;
@Schema: 'PLAYGROUND'
context unionDemo {
    entity E1 {
  key a : Integer;
  b : String(20);
  c : LocalDate;
entity E2 {
  key x : String(20);
  y : LocalDate;
  z : Integer;
view V as
  select from E1 { a, b, c}
  union
  select from E2 { z, x, y};