I ensure that my SQL view has the schema of NEC_LIVE which works with my database setup (you can also create views in X3 in the development section).  Then you can join the view like you would a table.

Allison Tentis  Thanks for your answer, but I don't quite understand. I'm new to this, and how can I find this view in SEI, for example?

If you can't add it to a data model when you are editing an "x3 database source" data model, then the schema is incorrect.  I think you whited out the schema in your screen shot, but I can only add views that are either NEC_LIVE (which is my nectari database) or LIVE.  See screen shot below

Allison Tentis Oh, that's exactly what I needed. Thank you!

Allison Tentis Oh, that's exactly what I needed. Thank you!