I need help with the follwing question:

Give an example of a column A and a column B such that B is functionally dependent on A. Give an example of a column C and a column D such that D is not functionally dependent on C.

I have an Excel worksheet in which I keep track of my expenditures by categories. I could rearrange my columns as follows:

Column A = Monthly income
Column B = What's left after subtracting (in other columns) total expenditures from total income.

Column C = Mortgage expenditure each month
Column D = Life insurance expenditure each month

Now you figure out the type of spreadsheet you can put together and what you would put in the various columns. If you need help using Excel or any other similar program, simply press the F1 key for the Help section.

need answer

To give an example of a column A and a column B where B is functionally dependent on A, let's consider a table representing employees in a company:

Column A: Employee ID
Column B: Employee Name

In this case, the employee name (B) is functionally dependent on the employee ID (A), as each unique employee ID corresponds to a specific employee name.

Now, let's provide an example of a column C and a column D where D is not functionally dependent on C. We can continue using the employee table example:

Column C: Employee ID
Column D: Employee Salary

In this case, the employee salary (D) is not functionally dependent on the employee ID (C). The reason is that different employees with the same employee ID might have different salaries, causing no direct relationship or dependency.

To answer the first part of your question, let me explain the concept of functional dependency. In a relational database, functional dependency refers to the relationship between two sets of attributes in a table. It means that the values in one set of attributes uniquely determine the values in another set of attributes.

For example, let's say we have a table called "Students" with the following columns: "StudentID", "First Name", "Last Name", and "Email". In this case, the StudentID column uniquely identifies each student, so "First Name", "Last Name", and "Email" are functionally dependent on the "StudentID" column. This means that if you know the value of "StudentID", you can determine the values of "First Name", "Last Name", and "Email".

Now, to provide an example as you requested, let's consider the table "Employees". Suppose we have two columns:
Column A: "EmployeeID"
Column B: "Salary"

In this case, if we assume that "EmployeeID" uniquely identifies each employee, then "Salary" is functionally dependent on "EmployeeID". Knowing the value of "EmployeeID" allows us to determine the salary of a particular employee.

Moving on to the second part of your question, let me explain an example where one column is not functionally dependent on another. Suppose we have another table called "Courses" with the following columns: "CourseID", "Course Name", "InstructorID", and "Instructor Name".

Column C: "CourseID"
Column D: "Instructor Name"

In this case, the "Instructor Name" is not functionally dependent on the "CourseID" because multiple courses can be taught by the same instructor. Knowing the "CourseID" alone does not uniquely determine the value of "Instructor Name". Therefore, we can say that "Instructor Name" is not functionally dependent on "CourseID".

I hope this explanation helps you understand functional dependency and provides you with the requested examples. Let me know if you have any further questions!