Recursive Query

ELI5 — The Vibe Check

A recursive query is SQL that calls itself, like a mirror reflecting a mirror. It's perfect for tree structures like org charts, comment threads, or category hierarchies. You give it a starting point and rules for finding the next level, and it keeps going until it runs out of matches.

Real Talk

A recursive query uses a recursive CTE (WITH RECURSIVE) to traverse hierarchical or graph-like data structures. It consists of an anchor member (base case) and a recursive member that references itself. PostgreSQL supports recursive CTEs for tree traversal, graph paths, and generating series. Cycle detection prevents infinite loops.

Show Me The Code

WITH RECURSIVE org_tree AS (
  SELECT id, name, manager_id, 1 AS depth
  FROM employees WHERE manager_id IS NULL
  UNION ALL
  SELECT e.id, e.name, e.manager_id, t.depth + 1
  FROM employees e
  JOIN org_tree t ON e.manager_id = t.id
)
SELECT * FROM org_tree ORDER BY depth;

When You'll Hear This

"We use recursive queries to traverse the entire category tree." / "Recursive CTEs are the SQL way to handle parent-child relationships."