[Solved] Given the table orders with columns customer_id and product, what will be the output of this query?SELECT customer_id, JSON_AGG(product) FROM orders GROUP BY customer_id ORDER BY customer_id; | PostgreSQL

PostgreSQL - Aggregate Functions and GROUP BY

Given the table orders with columns customer_id and product, what will be the output of this query?

SELECT customer_id, JSON_AGG(product) FROM orders GROUP BY customer_id ORDER BY customer_id;

AA single JSON array of all products ignoring customer_id

BEach customer_id with a JSON array of their products

CAn error because JSON_AGG cannot be used with GROUP BY

DEach product as a separate JSON object without aggregation

Step-by-Step Solution

Solution:

Step 1: Understand GROUP BY with JSON_AGG
The query groups rows by customer_id and aggregates the product values into JSON arrays per customer.
Step 2: Analyze output structure
Each row in the result shows a customer_id and a JSON array of products they ordered. No error occurs, and aggregation is per group.
Final Answer:
Each customer_id with a JSON array of their products -> Option B
Quick Check:
GROUP BY with JSON_AGG = grouped JSON arrays [OK]

Quick Trick: GROUP BY with JSON_AGG creates arrays per group [OK]

Common Mistakes:

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Given the table orders with columns customer_id and product, what will be the output of this query?