You want to list all customers and their orders, but also show customers with no orders. Which query correctly preserves all customers even if they have no orders?

hard📝 Application Q8 of 15

SQL - LEFT and RIGHT JOIN

ASELECT Customers.name, Orders.id FROM Orders LEFT JOIN Customers ON Customers.id = Orders.customer_id;

BSELECT Customers.name, Orders.id FROM Customers LEFT JOIN Orders ON Customers.id = Orders.customer_id;

CSELECT Customers.name, Orders.id FROM Customers INNER JOIN Orders ON Customers.id = Orders.customer_id;

DSELECT Customers.name, Orders.id FROM Customers RIGHT JOIN Orders ON Customers.id = Orders.customer_id;

Step-by-Step Solution

Solution:

Step 1: Identify which table to preserve
We want all customers, so Customers is the left table.
Step 2: Choose correct JOIN type and order
LEFT JOIN preserves all left rows; SELECT Customers.name, Orders.id FROM Customers LEFT JOIN Orders ON Customers.id = Orders.customer_id; uses LEFT JOIN with Customers as left table.
Final Answer:
SELECT Customers.name, Orders.id FROM Customers LEFT JOIN Orders ON Customers.id = Orders.customer_id; -> Option B
Quick Check:
LEFT JOIN with Customers left preserves all customers [OK]

Quick Trick: LEFT JOIN left_table preserves all left rows even if no match [OK]

Common Mistakes:

MISTAKES

Using INNER JOIN excludes customers without orders
Reversing table order in JOIN
Using RIGHT JOIN when LEFT JOIN is needed

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More SQL Quizzes

You want to list all customers and their orders, but also show customers with no orders. Which query correctly preserves all customers even if they have no orders?

Step 1: Identify which table to preserve

Step 2: Choose correct JOIN type and order

Final Answer:

Quick Check:

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