Was ist die äquivalente PostgreSQL-Syntax zu Oracles CONNECT BY ... START WITH?

Verwenden Sie einen RECURSIVE CTE in Postgres:

WITH RECURSIVE cte AS (
   SELECT key, value, 1 AS level
   FROM   taxonomy
   WHERE  key = 0

   UNION  ALL
   SELECT t.key, t.value, c.level + 1
   FROM   cte      c
   JOIN   taxonomy t ON t.taxHier = c.key
   )
SELECT value
FROM   cte
ORDER  BY level;

Details und Links zur Dokumentation in meiner vorherigen Antwort:

• Hat PostgreSQL eine Pseudo-Spalte wie "LEVEL" in Oracle?