W3. SQL Left Join

Question 1

Q: What does the SQL LEFT JOIN keyword do?

Answer 1

A: It returns all records from the left table and the matching records from the right table. If there’s no match, it returns 0 records from the right side.

Question 2

Q: Write the syntax for a LEFT JOIN.

Answer 2

SELECT column_name(s)
FROM table1
LEFT JOIN table2
ON table1.column_name = table2.column_name;

Question 3

Q: What is another name for LEFT JOIN in some databases?

Answer 3

A: LEFT OUTER JOIN

Question 4

Q: Write a query to select all customers and any orders they may have, sorted by CustomerName.

Answer 4

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID
ORDER BY Customers.CustomerName;

Question 5

Q: What happens in a LEFT JOIN if there is no matching record in the right table?

Answer 5

A: The result will include all records from the left table, and 0 (NULL) for columns from the right table with no match.