# Mastering SQL: Rounding Down Decimal Values for Employee Management

## Rounding Numbers: Understanding the Process

Have you ever found yourself struggling to figure out what the nearest whole number is when dealing with decimal numbers? Rounding is a common mathematical operation used to get an approximate whole number value for a decimal.

In this article, we’ll explore the concept of rounding numbers down to the nearest integer and how it can be useful in various situations.

## Understanding Flooring as a Mathematical Operation

Before jumping into rounding down, it is essential to understand the concept of flooring. In mathematics, flooring is a function that rounds any value down to the nearest integer.

The flooring function always rounds downwards, regardless of whether the decimal number is positive or negative. For example, the floor of 4.8 is 4, and the floor of -3.5 is -4.

This is different from the ceiling function which rounds up to the nearest integer. The flooring function is represented using the symbol ⌊x⌋, where x represents the input value.

The symbol looks like an upside-down L, with the input value in the middle. The flooring function can be used in various situations, such as when calculating the number of items required to complete a task or when determining the total cost of an item.

## Using FLOOR Function in SQL to Round Down

SQL is a popular programming language used to manage relational databases. It supports various mathematical functions, including the FLOOR function, which can be used to round down decimal numbers to the nearest integer.

The FLOOR function takes one parameter, which is the value to be rounded down. To use the FLOOR function in SQL, the syntax is as follows:

``` SELECT FLOOR(value) FROM table_name; ```

For example, let’s say we have a table named Salary with the following columns: EmployeeID and DailyPay.

We want to calculate the daily pay of each employee and round it down to the nearest integer. The SQL query would look something like this:

``` SELECT EmployeeID, FLOOR(DailyPay) as DailyPay FROM Salary; ```

This will provide a list of EmployeeIDs and their corresponding daily pay rounded down to the nearest integer.

## Calculating the Number of Days Worked by an Employee

Now that we understand how to round down decimal numbers, let’s apply it to calculating the number of days worked by an employee. In most cases, an employee’s daily pay is based on an eight-hour workday.

To calculate the number of days worked by an employee, we need to divide the total number of working hours by eight. For example, if an employee worked 36 hours in a week, we would calculate the number of days worked as follows:

``` Days Worked = FLOOR(36/8) Days Worked = FLOOR(4.5) Days Worked = 4 ```

This means that the employee worked for four full days and would have earned four days’ worth of pay.

### Assuming a Standard Eight-Hour Workday with No Irregularities

The above calculation assumes that the employee worked a standard eight-hour workday with no irregularities, such as overtime or a shorter workday. If an employee works overtime or has a shorter workday, the calculation for the number of days worked would need to be adjusted accordingly.

For example, if an employee worked six hours a day for three days and eight hours a day for two days, the calculation for the number of days worked would be as follows:

``` Days Worked = FLOOR(((6*3) + (8*2))/8) Days Worked = FLOOR(4.5) Days Worked = 4 ```

Even though the employee worked for five days, they only earned four days’ worth of pay because they did not complete a full eight-hour workday each day. In conclusion, rounding down decimal numbers to the nearest integer is a valuable mathematical skill that can be used in various situations.

Understanding the flooring function and using it in programming languages like SQL can help simplify calculations. When it comes to calculating the number of days worked by an employee, assuming a standard eight-hour workday with no irregularities is a good starting point, but adjustments may need to be made depending on the actual work hours.

## SQL Query to Show Employee Last Name, First Name, and Number of Days Worked

When managing employees, it can be helpful to obtain a list of employees and the number of days they have worked. In this article, we will explore how to use SQL to select specific columns from the employee table while also calculating the number of days an employee has worked.

### Selecting Required Columns from the Employee Table

To begin, we need to select the columns we are interested in from the employee table. In this case, we want to display an employee’s last name, first name, and the number of days worked.

The SQL code to select these columns would look something like this:

``` SELECT last_name, first_name, Days_Worked FROM employee; ```

By default, the output of this query will display every employee’s last name, first name, and Days_Worked, including those who have not worked any days.

### Using FLOOR Function in SQL Query for Day Calculation

Now, we need to calculate the number of days each employee has worked based on the hours they have logged. Similar to Subtopic 2.1, we can use the FLOOR function in SQL to round down the number of hours to the nearest full day.

Assuming we have a table named Hours_Worked which lists the hours worked by each employee, the SQL code to calculate the number of days worked would look like this:

``` SELECT employee.last_name, employee.first_name, FLOOR(SUM(Hours_Worked.hours)/8) as Days_Worked```

``` ```

``` FROM employee INNER JOIN Hours_Worked ON employee.employee_id = Hours_Worked.employee_id GROUP BY employee.last_name, employee.first_name; ```

In this code, we are using the SUM function to add up all the hours worked by each employee in the Hours_Worked table. We then divide this total by eight (assuming an eight-hour workday) and use the FLOOR function to round down the value to the nearest whole number.

Finally, we join the employee and Hours_Worked tables using the employee_id column, group the results by last name and first name, and display the last name, first name, and Days_Worked columns.

### Reviewing the SQL Query Result

When we execute the above SQL query, we get a list of all employees, including their last name, first name, and the number of days they have worked. The output would look something like this:

last_name first_name Days_Worked
Smith John 6
Doe Jane 3
Johnson Mark 2

The Days_Worked column indicates the number of days each employee worked, rounded down to the nearest whole number.

## Discussing Flooring and FLOOR Function in SQL

As we have seen, the FLOOR function is a valuable tool when working with decimal values in SQL and can be used to round down to the nearest whole number. Flooring is especially helpful when working with hours, as it allows us to calculate the number of days worked without the need for complex calculations.

In the example above, we calculated the number of days an employee worked based on a standard eight-hour workday. However, we can adjust this calculation if needed, such as if an employee works a different number of hours per day or if an organization has a different standard workday.

## In Conclusion

In this article, we have explored how to use SQL to select specific columns from the employee table and calculate the number of days worked by each employee. The Flooring function and the FLOOR function in SQL have proven to be helpful tools for simplifying calculations and rounding down decimal values to the nearest whole number.

These topics will help you stay organized and keep track of your employees’ work hours and days worked. In conclusion, this article explored the use of SQL to select specific columns from the employee table and calculate the number of days worked by each employee.

We learned about the Flooring function and the FLOOR function in SQL, which proved to be valuable tools for rounding down decimal values to the nearest whole number and making calculations more straightforward. Understanding these topics is essential for keeping track of employee work hours and can simplify many tasks related to employee management.

As a final thought, remember to adjust calculations based on any variations in working hours or company standards.