MySQL多列求和的平均值

Question

I have a mysql query to build that is giving me a little trouble. I have completed what I need with a slew of queries put together, but I know there must be a better way.

I have a survey answer table, with 5 columns for answers to 5 questions. The questions are always from 1(lowest) to 5(highest).

I need to find the average of all 5 answers and display as a percentage out of 100%.

At first, I accomplished this by:

Select qone,qtwo,qthree,qfour,qfive FROM survey_answers WHERE survey_id='$survey_id'

Then as I loop through all answers:

$counter++;
$survey_total = $survey_total+(($qone+$qtwo+$qthree+$qfour+$qfive)/25);

Finally, after looping through all survey results:

$total_average = $survey_total/$counter;

So this is how I solve what I need to do.

Can anyone help me refine this query, maybe even into one?

Is it possible to do something like:

Select AVG(SUM(qone+qtwo+qthree+qfour+qfive)/25)) FROM survey_answers WHERE survey_id='$survey_id'

The above query does not work, and I know sum counts all rows of that column name. Is there MySQL syntax to add up multiple columns of the same entry? Also, if there is, may I divide that sum by a number I choose, then average those results in one query??

Thank you. Jason

Answer 1

Try something like this, that should give you the result you're looking for in %

SELECT 
 20 * q1 / devider AS Question1, 
 20 * q2 / devider AS Question2, 
 20 * q3 / devider AS Question3, 
 20 * q4 / devider AS Question4, 
 20 * q5 / devider AS Question5
FROM (
 SELECT (
  SELECT COUNT( survey_id ) 
   FROM (
    SELECT survey_id
    FROM `survey_answers`
    WHERE  `survey_id` ='$survey_id'
    )tt1
   ) AS devider, SUM(`qone') AS q1, SUM(`qtwo`) as q2, SUM(`qthree`) as q3, SUM(`qfour`) as q4, SUM(`qfive`) AS q5
   FROM  `survey_answers` 
   WHERE  `survey_id` ='$survey_id'
   GROUP BY  `survey_id`
  )tt2