[Solved] Find the mistake in this recursive CTE:WITH RECURSIVE cte(node) AS ( SELECT node FROM graph WHERE node = 1 UNION ALL SELECT node + 1 FROM cte WHERE node | PostgreSQL

PostgreSQL - Common Table Expressions

Find the mistake in this recursive CTE:

WITH RECURSIVE cte(node) AS ( SELECT node FROM graph WHERE node = 1 UNION ALL SELECT node + 1 FROM cte WHERE node <= 5 ) SELECT * FROM cte;

ACTE name conflicts with table name

BAnchor member selects wrong column

CRecursive member should use UNION instead of UNION ALL

DRecursive member condition allows infinite recursion

Step-by-Step Solution

Solution:

Step 1: Analyze recursive member condition
The condition 'node <= 5' includes 5, so recursion continues when node=5.
Step 2: Check if recursion stops
Since node increments by 1, it will go beyond 5, but condition allows node=5 again, causing infinite loop.
Final Answer:
Recursive member condition allows infinite recursion -> Option D
Quick Check:
Recursive condition must prevent infinite loops [OK]

Quick Trick: Use strict less than to stop recursion safely [OK]

Common Mistakes:

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Find the mistake in this recursive CTE: