Calculating Percentage in MySQL

Within a MySQL database containing employee and survey data, a user sought to calculate the percentage of employees who participated in surveys based on the number of recorded surveys.

The original query attempted to derive the percentage using the following statement:

SELECT
  group_name,
  employees,
  surveys,
  COUNT( surveys ) AS test1, 
  ((COUNT( * ) / ( SELECT COUNT( * ) FROM a_test)) * 100 ) AS percentage
FROM
  a_test
GROUP BY
  employees

However, this approach yielded incorrect results. To rectify the issue, a revised query was proposed:

   SELECT group_name, employees, surveys, COUNT( surveys ) AS test1, 
        concat(round(( surveys/employees * 100 ),2),'%') AS percentage
    FROM a_test
    GROUP BY employees

This modified query incorporates the following adjustments:

• Correct Calculation: The percentage is now calculated as ( surveys / employees * 100 ), providing the accurate proportion of surveyed employees.
• Percentage Formatting: The result is formatted as a percentage string using concat and round functions to display a rounded percentage with two decimal places.