CDS view "All fields are evaluated as key field"

Hi all,

I have defined a CDS view like

select

{ key crmd_orderadm_h.col1, crmd_srv_subject.col2, crmd_srv_subject2.col3 }

where

I just specified one key which is col1, but I got the warning.

And in SE11, I saw all three columns are keys.

Anyone knows something about that?