[Solved] Find the problem in this query:SELECT * FROM products WHERE EXISTS (SELECT * FROM orders WHERE orders.product_id = products.id AND orders.quantity); | PostgreSQL

PostgreSQL - Subqueries in PostgreSQL

Find the problem in this query:

SELECT * FROM products WHERE EXISTS (SELECT * FROM orders WHERE orders.product_id = products.id AND orders.quantity);

AMissing JOIN between products and orders

Bproducts.id is not a valid column

CEXISTS cannot use SELECT * inside subquery

DThe condition 'orders.quantity' is incomplete and may cause unexpected results

Step-by-Step Solution

Solution:

Step 1: Review the subquery condition
The condition 'orders.quantity' alone is incomplete; it checks if quantity is true (non-zero), which may be unintended.
Step 2: Understand impact on EXISTS
This may cause unexpected filtering because it treats quantity as a boolean, not a comparison.
Final Answer:
The condition 'orders.quantity' is incomplete and may cause unexpected results -> Option D
Quick Check:
Incomplete condition causes logic errors = B [OK]

Quick Trick: Always use full conditions like 'quantity > 0' in EXISTS subqueries [OK]

Common Mistakes:

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