Which SQL command is used to define a new index on a table to improve query performance?
Question 2
Consider a database with two tables: \texttt{Employees} (\texttt{EmployeeID}, \texttt{Name}, \texttt{DepartmentID}) and \texttt{Departments} (\texttt{DepartmentID}, \texttt{DepartmentName}). Which SQL query would return the \texttt{Name} of all employees and their corresponding \texttt{DepartmentName}, including employees who are not assigned to any department?
Question 3
Which of the following SQL queries would correctly retrieve the names of customers who have placed more than 5 orders, assuming an \texttt{Orders} table with \texttt{CustomerID} and an \texttt{Customers} table with \texttt{CustomerID} and \texttt{CustomerName}?
Question 4
What is the purpose of the \texttt{CASE} statement in SQL?
Question 5
Consider a table named \texttt{Sales} with columns \texttt{ProductID}, \texttt{SaleDate}, and \texttt{Amount}. Which SQL query would calculate the total \texttt{Amount} for each \texttt{ProductID} for sales made in the year 2023?
