I am trying to define a CTE and then immediately use it in a WHERE clause using the IN operator.

This does NOT work.

WITH T AS (SELECT 1)
SELECT 2 WHERE 1 IN T;

This does work, but I need to add a SELECT.

WITH T AS (SELECT 1)
SELECT 2 WHERE 1 IN (SELECT * FROM T);

Is there a way to get rid of the last SELECT?

I am using this query in the context of Foreign Data wrappers. The addition of the last select prevents the "in-lining" of the intermediate results.