You want to list all customers and their orders, but some customers may have no orders. Which query is correct?

hard📝 Application Q9 of 15

SQL - LEFT and RIGHT JOIN

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

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

Step-by-Step Solution

Solution:

Step 1: Identify which table to keep all rows from
We want all customers listed, even if no orders, so keep all Customers rows.
Step 2: Choose JOIN type
LEFT JOIN keeps all rows from the left table (Customers) and matches from Orders.
Step 3: Verify query syntax
SELECT Customers.name, Orders.id FROM Customers LEFT JOIN Orders ON Customers.id = Orders.customer_id; uses Customers LEFT JOIN Orders ON Customers.id = Orders.customer_id, which is correct.
Final Answer:
SELECT Customers.name, Orders.id FROM Customers LEFT JOIN Orders ON Customers.id = Orders.customer_id; -> Option B
Quick Check:
Keep all customers = LEFT JOIN with Customers as left table [OK]

Quick Trick: LEFT JOIN keeps all left table rows, unmatched right columns NULL [OK]

Common Mistakes:

MISTAKES

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