Yeah, I think composability is one of the biggest things missing from SQL.

The issue is that composability is often tied to actually moving data around in the database which has terrible performance. That is, you can compose a query of multiple queries that dump partial data sets into temp tables.

Views get you part of the way there, but they are designed to be long lived and are visible to all database users until they are dropped. This means its dangerous to change them or clean them up, as its not always clear who they are being used by.

Ephermal or temporary views that are session/connection based, or even loadable as modules would be useful to me.