[Solved] Given the table orders with columns customer_id and order_amount, what will this query return?SELECT customer_id, COUNT(*), SUM(order_amount) FROM orders GROUP BY customer_id; | SQL

SQL - GROUP BY and HAVING

Given the table orders with columns customer_id and order_amount, what will this query return?

SELECT customer_id, COUNT(*), SUM(order_amount) FROM orders GROUP BY customer_id;

ASyntax error due to missing WHERE clause

BTotal orders for all customers combined

CList of customers without any aggregation

DNumber of orders and total amount per customer

Step-by-Step Solution

Solution:

Step 1: Understand the query components
The query groups rows by customer_id, counts orders per customer, and sums order amounts per customer.
Step 2: Interpret the output
Each row shows a customer_id, number of orders, and total order amount for that customer.
Final Answer:
Number of orders and total amount per customer -> Option D
Quick Check:
GROUP BY with COUNT and SUM = Aggregated per group [OK]

Quick Trick: GROUP BY aggregates per group, not entire table [OK]

Common Mistakes:

MISTAKES

Thinking COUNT(*) counts all rows ignoring GROUP BY
Expecting total for all customers in one row
Assuming WHERE is required for GROUP BY

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More SQL Quizzes

Given the table orders with columns customer_id and order_amount, what will this query return?

Step 1: Understand the query components

Step 2: Interpret the output

Final Answer:

Quick Check:

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