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

SQL - GROUP BY and HAVING

Given a table orders with columns customer_id and amount, what will this query return?

SELECT customer_id, SUM(amount) FROM orders GROUP BY customer_id;

ATotal amount spent by each customer

BTotal amount spent by all customers combined

CList of customers without totals

DError because SUM() needs no GROUP BY

Step-by-Step Solution

Solution:

Step 1: Understand GROUP BY with SUM()
The query groups rows by customer_id and sums amounts per group.
Step 2: Interpret the output
Each row shows a customer and their total spending.
Final Answer:
Total amount spent by each customer -> Option A
Quick Check:
GROUP BY customer_id + SUM = totals per customer [OK]

Quick Trick: GROUP BY groups rows; SUM calculates per group [OK]

Common Mistakes:

MISTAKES

Thinking SUM totals all rows without grouping
Expecting list without totals
Assuming query causes error

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More SQL Quizzes

Given a table orders with columns customer_id and amount, what will this query return?

Step 1: Understand GROUP BY with SUM()

Step 2: Interpret the output

Final Answer:

Quick Check:

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