SELECT 1 FROM z;
SELECT 1 FROM c.db.z AS z;

SELECT 1 FROM y.z;
SELECT 1 FROM c.y.z AS z;

SELECT 1 FROM x.y.z;
SELECT 1 FROM x.y.z AS z;

SELECT 1 FROM x.y.z AS z;
SELECT 1 FROM x.y.z AS z;

WITH a AS (SELECT 1 FROM z) SELECT 1 FROM a;
WITH a AS (SELECT 1 FROM c.db.z AS z) SELECT 1 FROM a;

SELECT (SELECT y.c FROM y AS y) FROM x;
SELECT (SELECT y.c FROM c.db.y AS y) FROM c.db.x AS x;