Solution:Step 1: Understand the requirementWe want customers who placed orders and the total amount spent, so INNER JOIN with aggregation is needed.Step 2: Analyze each optionSELECT c.customer_name, SUM(o.amount) AS total_spent FROM Customers c INNER JOIN Orders o ON c.customer_id = o.customer_id GR

[Solved] You have two tables:Orders(order_id, customer_id, amount)Customers(customer_id, customer_name)You want to find all customers who have placed orders and the total amount they spent.... | SQL

SQL - INNER JOIN

You have two tables:
Orders(order_id, customer_id, amount)
Customers(customer_id, customer_name)
You want to find all customers who have placed orders and the total amount they spent.
Which query correctly uses INNER JOIN and aggregation to get this result?

ASELECT c.customer_name, SUM(o.amount) AS total_spent FROM Customers c LEFT JOIN Orders o ON c.customer_id = o.customer_id GROUP BY c.customer_name;

BSELECT c.customer_name, o.amount FROM Customers c INNER JOIN Orders o ON c.customer_id = o.customer_id;

CSELECT c.customer_name, SUM(o.amount) AS total_spent FROM Customers c INNER JOIN Orders o ON c.customer_id = o.customer_id GROUP BY c.customer_name;

DSELECT customer_name, amount FROM Customers INNER JOIN Orders ON customer_id = customer_id;

Step-by-Step Solution

Solution:

Step 1: Understand the requirement
We want customers who placed orders and the total amount spent, so INNER JOIN with aggregation is needed.
Step 2: Analyze each option
SELECT c.customer_name, SUM(o.amount) AS total_spent FROM Customers c INNER JOIN Orders o ON c.customer_id = o.customer_id GROUP BY c.customer_name; correctly uses INNER JOIN on customer_id and sums amounts grouped by customer_name. SELECT c.customer_name, SUM(o.amount) AS total_spent FROM Customers c LEFT JOIN Orders o ON c.customer_id = o.customer_id GROUP BY c.customer_name; uses LEFT JOIN, which includes customers without orders. SELECT c.customer_name, o.amount FROM Customers c INNER JOIN Orders o ON c.customer_id = o.customer_id; does not aggregate amounts. SELECT customer_name, amount FROM Customers INNER JOIN Orders ON customer_id = customer_id; has ambiguous join condition and no aggregation.
Final Answer:
SELECT c.customer_name, SUM(o.amount) AS total_spent FROM Customers c INNER JOIN Orders o ON c.customer_id = o.customer_id GROUP BY c.customer_name; -> Option C
Quick Check:
INNER JOIN + GROUP BY + SUM = total spent per customer [OK]

Quick Trick: Use INNER JOIN with GROUP BY and SUM for totals [OK]

Common Mistakes:

MISTAKES

Using LEFT JOIN instead of INNER JOIN when only matching rows needed
Forgetting GROUP BY with aggregation
Incorrect join condition syntax

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