Bug Report for sql-customers-bought-a-b-not-c

[sidAKAsadiq]

Bug Description

When using a LEFT JOIN with a subquery as the left table, the output display
incorrectly renders the left table's customer_id as null instead of its
actual value.

Steps to Reproduce

1. Go to: https://neetcode.io/problems/sql-customers-bought-a-b-not-c
2. Run the following query:

SELECT o12., o3.
FROM (
SELECT o1.customer_id
FROM (SELECT * FROM orders WHERE product_name = 'A') AS o1
INNER JOIN (SELECT * FROM orders WHERE product_name = 'B') AS o2
ON o1.customer_id = o2.customer_id
) AS o12
LEFT JOIN (SELECT * FROM orders WHERE product_name = 'C') AS o3
ON o12.customer_id = o3.customer_id;

Expected Output

customer_id (o12) | order_id | customer_id (o3) | product_name
1 | 104 | 1 | C
3 | null | null | null

Actual Output

customer_id | order_id | customer_id | product_name
1 | 104 | 1 | C
null | null | null | null

Impact

The left side of a LEFT JOIN should never be null. This misleading display
causes confusion about query correctness, as the actual JOIN logic works
correctly when further joined with the customers table.