Solution:Step 1: Understand CTE materialization and cross joinThe CTE generates numbers 1 to 3 and is materialized once. The main query cross joins with generate_series(1,2).Step 2: Calculate output rowsEach num (1,2,3) pairs with gs.n (1,2), producing 6 rows: (1,1), (1,2), (2,1), (2,2), (3,1), (3,2

[Solved] Given the query:WITH cte AS MATERIALIZED (SELECT generate_series(1,3) AS num) SELECT num FROM cte, generate_series(1,2) AS gs(n);What is the output? | PostgreSQL

PostgreSQL - Common Table Expressions

Given the query:

WITH cte AS MATERIALIZED (SELECT generate_series(1,3) AS num) SELECT num FROM cte, generate_series(1,2) AS gs(n);

What is the output?

ARows: (1,1), (1,2), (2,1), (3,1), (3,2)

BRows: (1,1), (2,1), (3,1)

CRows: (1,1), (1,2), (2,1), (2,2), (3,1), (3,2)

DRows: (1,1), (2,2), (3,1), (3,2)

Step-by-Step Solution

Solution:

Step 1: Understand CTE materialization and cross join
The CTE generates numbers 1 to 3 and is materialized once. The main query cross joins with generate_series(1,2).
Step 2: Calculate output rows
Each num (1,2,3) pairs with gs.n (1,2), producing 6 rows: (1,1), (1,2), (2,1), (2,2), (3,1), (3,2).
Final Answer:
Rows: (1,1), (1,2), (2,1), (2,2), (3,1), (3,2) -> Option C
Quick Check:
Materialized CTE cross join = all combinations [OK]

Quick Trick: Materialized CTE runs once; cross join multiplies rows [OK]

Common Mistakes:

Assuming CTE runs multiple times
Ignoring cross join effect
Counting fewer rows than actual

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Given the query:

Step 1: Understand CTE materialization and cross join

Step 2: Calculate output rows

Final Answer:

Quick Check:

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