[Solved] What will be the result of this query?WITH RECURSIVE nums AS (SELECT 1 AS n UNION ALL SELECT n+1 FROM nums WHERE n | PostgreSQL

PostgreSQL - Advanced Features

What will be the result of this query?
WITH RECURSIVE nums AS (SELECT 1 AS n UNION ALL SELECT n+1 FROM nums WHERE n < 3) SELECT * FROM nums;

AAn infinite loop error

BRows with n values: 1, 2, 3

CNo rows returned

DRows with n values: 1 only

Step-by-Step Solution

Solution:

Step 1: Understand recursive CTE behavior
The CTE starts with n=1, then adds n+1 while n < 3.
Step 2: Trace recursion steps
n=1, then 2, then 3; recursion stops after n=3.
Step 3: Final output
Query returns rows with n = 1, 2, and 3.
Final Answer:
Rows with n values: 1, 2, 3 -> Option B
Quick Check:
Recursive CTE output = Rows with n values: 1, 2, 3 [OK]

Quick Trick: Recursive CTEs stop when WHERE condition fails [OK]

Common Mistakes:

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What will be the result of this query?