2.2. LEFT JOIN

Try these first

1. 1.

   What does a LEFT JOIN do in SQL?

   Hint

   Think about the tables involved and which records are included.

2. 2.

   In which scenario would you prefer using LEFT JOIN over INNER JOIN?

   Hint

   Consider what happens when there's missing data.

3. 3.

   What does LEFT JOIN return when there are no matching records in the right table?

   • Only matching records
   • All records from the left table
   • No records

   Hint

   Consider what LEFT stands for in LEFT JOIN.

4. 4.

   True or False: LEFT JOIN omits records from the left table if there are no matches in the right table.

   • True
   • False

   Hint

   Reflect on the definition and purpose of LEFT JOIN.

5. 5.

   Suppose you have two tables: 'employees' and 'departments'. Write a LEFT JOIN query to list all employees and their departments, ensuring to include employees who might not belong to any department.

   Hint

   Consider how employees relate to departments.

6. 6.

   Imagine you are analyzing a customer database where some customers have not made any purchases. Formulate a LEFT JOIN query that tallies the purchases made by each customer and returns all customers regardless of whether they made a purchase or not.

   Hint

   Remember to group your results to get counts.