SQL 5 – Quiz | Divex Consult

1. What is the purpose of an INNER JOIN in SQL? *

A) Returns all rows from both tables

B) Returns only matching rows from both tables

C) Returns all rows from the left table and matching rows from the right table

D) Returns all rows from the right table and matching rows from the left table

2. Which SQL statement retrieves all customers who have placed at least one order? *

A) SELECT Customers.Customer_ID, Customers.First_Name, Orders.Order_ID FROM Customers LEFT JOIN Orders ON Customers.Customer_ID = Orders.Customer_ID;

B) SELECT Customers.Customer_ID, Customers.First_Name, Orders.Order_ID FROM Customers RIGHT JOIN Orders ON Customers.Customer_ID = Orders.Customer_ID;

C) SELECT Customers.Customer_ID, Customers.First_Name, Orders.Order_ID FROM Customers INNER JOIN Orders ON Customers.Customer_ID = Orders.Customer_ID;

D) SELECT Customers.Customer_ID, Customers.First_Name, Orders.Order_ID FROM Customers FULL OUTER JOIN Orders ON Customers.Customer_ID = Orders.Customer_ID;

3. What does a LEFT JOIN return? *

A) Only matching rows from both tables

B) All rows from the left table and matching rows from the right table

C) All rows from the right table and matching rows from the left table

D) All rows from both tables, whether they match or not

4. What happens when there is no match in a LEFT JOIN? *

A) The row from the left table appears with NULL values for columns from the right table

B) The row from the left table is excluded

C) The row from the right table appears with NULL values for columns from the left table

D) The row is removed from the result set

5. What does a RIGHT JOIN do? *

A) Returns only matching rows from both tables

B) Returns all rows from the left table and matching rows from the right table

C) Returns all rows from the right table and matching rows from the left table

D) Returns all rows from both tables

6. What does a FULL OUTER JOIN return? *

A) Only matching rows from both tables

B) All rows from both tables, with NULL where there is no match

C) All rows from the left table and matching rows from the right table

D) All rows from the right table and matching rows from the left table

7. Which JOIN is most appropriate when you want to keep all records from both tables? *

A) INNER JOIN

B) LEFT JOIN

C) RIGHT JOIN

D) FULL OUTER JOIN

8. What does this query do?
SELECT Customers.Customer_ID, Customers.First_Name, Orders.Order_ID
FROM Customers
RIGHT JOIN Orders ON Customers.Customer_ID = Orders.Customer_ID; *

A) Returns all customers and their orders

B) Returns only customers who have placed orders

C) Returns all orders and their customers, including orders without customers

D) Returns only orders that have customers

9. Which JOIN type is used when retrieving all customers, including those who haven't placed orders? *

A) INNER JOIN

B) LEFT JOIN

C) RIGHT JOIN

D) FULL OUTER JOIN

10. How can you filter results after using a JOIN? *

A) Use the HAVING clause

B) Use the ORDER BY clause

C) Use the WHERE clause

D) Use the GROUP BY clause

Structured Query Language(SQL)

SQL 5 – Quiz