SQL Queries

Here's a sample data structure for the "employees" table that you can use to solve the queries:

| employee_id | name      | age | department | salary |

|-------------|-----------|-----|------------|--------|

| 1           | John      | 30  | sales      | 50000  |

| 2           | Emily     | 35  | finance    | 60000  |

| 3           | Michael   | 40  | sales      | 55000  |

| 4           | Sarah     | 28  | finance    | 62000  |

| 5           | David     | 45  | HR         | 48000  |

| 6           | Jessica   | 32  | sales      | 51000  |

| 7           | Andrew    | 38  | finance    | 58000  |

| 8           | Olivia    | 29  | HR         | 47000  |

Here are five SQL query questions for you to solve:

1. **Retrieve all columns from the "employees" table:**

2. **Retrieve the names and ages of all employees from the "employees" table:**

3. **Retrieve the names of all employees who are in the "sales" department from the "employees" table:**

4. **Count the number of employees in the "finance" department from the "employees" table:**

5. **Retrieve the names and salaries of all employees from the "employees" table, ordered by salary in descending order:**

1. Write a query to find the average salary of all employees.
2. Retrieve the maximum salary from the finance department.
3. Get the total number of employees in each department.
4. Find the employee with the highest salary.
5. Calculate the average age of employees in the HR department.

Here are five questions where you would need to use the `GROUP BY` clause:

1. **Average Salary by Department:**

   Write a query to find the average salary of employees in each department.

2. **Total Number of Employees by Department:**

   Retrieve the total number of employees in each department.

3. **Maximum Salary by Age Group:**

   Get the maximum salary for employees grouped by age ranges (e.g., 20-30, 31-40, etc.).

4. **Count of Employees by Department and Age Group:**

   Find the count of employees grouped by department and age ranges.

5. **Total Salary Expenses by Department:**

   Calculate the total salary expenses for each department.

These questions require grouping data based on specific criteria, such as department, age group, etc., to perform aggregate functions like `AVG`, `COUNT`, `MAX`, and `SUM`.

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