The *PERCENT_RANK()* function is used in SQL to calculate the relative rank of a row within a result set as a percentage. It returns a value between 0 and 1, representing the percentile of a specific row in relation to the entire dataset.
The formula for *PERCENT_RANK()* is:
PERCENT_RANK() = (rank - 1) / (total_rows - 1)

Where:
- *rank* is the rank of the row (1 for the highest rank).
- *total_rows* is the total number of rows in the partition.
###### Usage

To use the *PERCENT_RANK()* function, you typically follow these steps:
1. **Select the dataset**: Decide which dataset you want to analyze.
2. **Choose an ordering**: Determine how you want to rank the rows (e.g., based on sales, scores, or any numeric field).
3. **Use the function**: Incorporate *PERCENT_RANK()* into your SQL query.
###### Example

Here’s an example of using *PERCENT_RANK()* to find the percent rank of employees based on their salary:
SELECT
employee_id,
salary,
PERCENT_RANK() OVER (ORDER BY salary) AS percent_rank
FROM
employees;

###### Explanation of the example:

- *employee_id* and *salary* are selected from the *employees* table.
- The *PERCENT_RANK()* function is applied with *OVER (ORDER BY salary)*, which calculates the rank based on the *salary* column in ascending order.
- The result of *PERCENT_RANK()* is included as a new column labeled *percent_rank*.
###### Notes:

- If all rows have the same value for the column used in the ordering, *PERCENT_RANK()* will return a value of 0 for all of these rows.
- The results are typically used in conjunction with other analytical functions or as part of further data analysis.
Make sure that your SQL database supports window functions, as not all database systems may include them or use the same syntax.