How to do the math in sql query to calculate percentage difference?

Question

I would like to conduct surveys (2 or more options) and put the results in a table. I just want to know how I could count the results in a sql query.

Even more, should I do the math in the query or just use PHP to do the math?

Example

Table of questions

question_id (int) question (text) answer_1 (varchar) answer_2 (varchar) answer_3 (varchar) etc... 

Answer Table

 answer_id (int) question_id (int) answer (int) The answer they chose. (1, 2, 3, etc.) 

How should I / I calculate the results?

Edit: using MySQL, PHP. The difference between the answers (45% said blah, 50% said blah blah, 5% said they were flea). Not for homework, Im EE, not CS

Answer 1

If the number of answers is not known in advance, it would be easier to divide the question table into 2 - one for questions (question_id, question_text) and one for choice (question_id, choice_id, choice_text). An answer table can be executed (question_id, answer_id, choice_id). Then, choosing it, something like the following will be used (QID = identifier of the question you are choosing):

 SELECT choice, (COUNT(*) / (SELECT COUNT(*) FROM answers WHERE answers.question_id = QID)) * 100 AS percentage FROM choices INNER JOIN answers ON choices.choice_id = answers.choice_id AND choices.question_id AND choices.question_id WHERE choices.question_id = QID GROUP BY choice_id; 

All this means that the total number of answers in the internal query, and then for each choice, divide the number of answers with this choice compared to the total.

Answer 2

This will allow you to choose the popularity of each answer in the question:

 SELECT question, COUNT(*) / ( SELECT COUNT(*) FROM answers ai WHERE ai.question = a.question ) FROM answers a GROUP BY question, answer 

It will not select answers if they have never been given.

Answer 3

 select answer, count(*) from Answers where answer_id = 1 group by answer 

or

 select answer_id,answer, count(*) from Answers group by answer_id, answer 

I would give you a request that takes into account the answers to each question, but, unfortunately, you have no way to link the answers to the questions. Neither do you need to answer answer_1, answer_2, etc. In the table of questions. You need to normalize the table. If you do not understand how to do this, you need to learn before designing a database.