Code Inspection: Unused common table expression

Reports unused common table expressions (CTE) inside the query.

Example (PostgreSQL):

CREATE TABLE foo(a INT);

WITH a AS (SELECT 1 AS x FROM foo)
SELECT 1 + 2 FROM foo;

By using WITH, we create a temporary named result set with the name a, also known as a common table expression (CTE). But we do not use this CTE later in the code. The unused CTE is greyed out.