Exercise 1: Testing getBreadcrumb() at Three Levels — Possible Solution
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SETUP
------------------------------
  id: 1, title: 'Programming',              parent_id: NULL
  id: 2, title: 'General-Purpose Languages', parent_id: 1
  id: 3, title: 'Java',                      parent_id: 2

async function getBreadcrumb(pool, pageId) {
  const [rows] = await pool.query(`
    WITH RECURSIVE ancestors AS (
      SELECT *, 0 AS depth FROM pages WHERE id = ?
      UNION ALL
      SELECT p.*, a.depth + 1 FROM pages p
      INNER JOIN ancestors a ON p.id = a.parent_id
    )
    SELECT * FROM ancestors ORDER BY depth DESC;
  `, [pageId]);
  return rows;
}

await getBreadcrumb(pool, 3);

RESULT
------------------------------
[
  { id: 1, title: 'Programming', depth: 2, ... },
  { id: 2, title: 'General-Purpose Languages', depth: 1, ... },
  { id: 3, title: 'Java', depth: 0, ... }
]

- root-to-leaf order, exactly matching what every sibling course's
own breadcrumb needed, produced here by a single query instead of
three separate ones or a nested eager-load call.

WHY THIS WORKS AS AN ANSWER
------------------------------
It correctly calls getBreadcrumb() with a real three-level-deep page
ID, and correctly shows the resulting array in the proper
root-to-leaf order the recursive CTE's own depth-based ordering
produces.