CODEWITHSUNDEEP
phpmysqlsqlpivot
Ralph
Ralph

Reputation: 132

Pivot table in a specific way in MySQL

There are other pivot table questions but I can't seem to find an answer to my question.

This is my table

ID    QUESTION       ANSWER       RECORDID      SORTORDER
1     Question 1     Answer 1.1   123456        1
2     Question 2     Answer 2.1   123456        2
3     Question 3     Answer 3.1   123456        3
4     Question 1     Answer 1.2   654321        1
5     Question 2     Answer 2.2   654321        2
6     Question 3     Answer 3.2   654321        3

Etc.

I would like to output it with a query to:

Question 1    Question 2    Question 3
Answer 1.1    Answer 2.1    Answer 3.1
Answer 1.2    Answer 2.2    Answer 3.2

So in short, the question column holds questions that are not unique (in this demo there are 2 entries (see RECORDID)) so they need to be grouped and sorted by sortorder. RECORDID is always unique

I've seen some pivot/unpivot examples but can't get my head around it. Can someone help me with this?

Upvotes: 1

Views: 90

Answers (2)

Ralph
Ralph

Reputation: 132

Thank you all (especially Koshera!), with some tweaking I got it to work the way I wanted it.

This is the total code (raw, proof of concept;)). The function processQuery is a try / catch PDO execution with parameterized query (see the ? placeholder, the "raw" $i shouldn't be a problem?).

<div class="database-container">
<table border="0" cellspacing="0" cellpadding="7">
<tr>

<?php

// get all questions and group them so we only get unique questions
$getQuestions = processQuery("SELECT ansr_question FROM forms_123456 WHERE is_answer=1 and ansr_type != 'text' GROUP BY ansr_question ORDER BY ansr_sortorder ASC",$param,'fetch-raw',$server,$extra,$DBH);
unset($param);

// fetch all the questions
while($fetchQuestions = $getQuestions->fetch())

    {

        // save into array and generate the column questions
        $questions[] = $fetchQuestions["ansr_question"];
        $question_headers .= '<td height="19" nowrap style="background-color:#e9e9e9; font-weight:400;">'.trim(ucfirst($fetchQuestions["ansr_question"])).'</td>';

    }

// loop array
$num_questions = count($questions);
$num_questions_check = $num_questions -1;
for($i=0; $num_questions > $i; ++$i)

    {

    // prepare PDO params
    $param[] = $questions[$i];

    // use the count to perform if statement when last question has been reached
    $comma = ',';
    if($num_questions_check == $i)

        {
        $comma = '';
        }

    // generate the 2 dynamic parts of the query
    $sql_part1 .= "max(qq.question$i) as 'answer$i',";
    $sql_part2 .= "case when q.ansr_question = ? then ansr_answer else null end as question$i$comma ";

    }


// make it 1 query
$query = "select 
$sql_part1
ansr_recordid, 
ansr_type
FROM (
    SELECT
        ansr_recordid, 
        ansr_type,
        $sql_part2
    FROM(
        select 
            ansr_recordid, 
            ansr_question,
            ansr_answer,
            ansr_type,
            ansr_sortorder
            from forms_123456 where is_answer=1 order by ansr_recordid, ansr_sortorder 
            ) q
    )qq
GROUP BY ansr_recordid";

// lets try it!
$getAnswers = processQuery($query,$param,'fetch-raw',$server,$extra,$DBH);
unset($param);


// show questions and other data
echo '<td height="19" nowrap style="background-color:#e9e9e9; font-weight:600;">Status</td>
    <td height="19" nowrap style="background-color:#e9e9e9; font-weight:600;">Details</td>';

echo $question_headers;

echo '<td height="19" nowrap style="background-color:#e9e9e9; font-weight:600;">Record ID</td>
    <td height="19" nowrap style="background-color:#e9e9e9; font-weight:600;">Start Date</td>
    <td height="19" nowrap style="background-color:#e9e9e9; font-weight:600;">End Date</td>
</tr>';


// show values ----------------------------------------
$first = 1;
while($fetch = $getAnswers->fetch())

{

// change color per row
if($first == 0)

    {
    $first = 1;
    $bgcolor = '#f1f1f1';
    }
else
    {
    $first = 0;
    $bgcolor = '';
    }

echo '<tr>';

echo '<td height="19" nowrap style="background-color:'.$bgcolor.'; font-weight:400;">OK</td>
    <td height="19" nowrap style="background-color:'.$bgcolor.'; font-weight:400;">Bekijken</td>';

// loop the number of questions so we get the same amount of columns
for($i=0; $num_questions > $i; ++$i)

    {
    echo '<td height="19" nowrap style="background-color:'.$bgcolor.'; font-weight:400;">'.trim(ucfirst($fetch["answer$i"])).'</td>';
    }

echo '<td height="19" nowrap style="background-color:'.$bgcolor.'; font-weight:400;">'.$fetch["ansr_recordid"].'</td>
    <td height="19" nowrap style="background-color:'.$bgcolor.'; font-weight:400;">Start Date</td>
    <td height="19" nowrap style="background-color:'.$bgcolor.'; font-weight:400;">End Date</td>';

echo '</tr>';

}

?>

</table>
</div>

Upvotes: 1

Koshera
Koshera

Reputation: 449

This should do the trick. In the inner query you get only the answers for the specific question and in the outer query when you group by the recordid you get rid of the null values... Try running only the inner query to get the idea. 

select  
  max(q.Question1),
  max(q.Question2),
  max(q.Question3) FROM (SELECT     
                         recordid,
                         case when question = 'Question 1' then answer else null end as Question1, 
                         case when question = 'Question 2' then answer else null end as Question2, 
                         case when question = 'Question 3' then answer else null end as Question3 FROM questions) q group by q.recordid

Let me know if you have any quesitons!

EDIT: Your comment adds another level of complexity :) Now I see how we can use that sort order column... We need one more inner query to get the questions and their sort order. Then get the answers per each sort order and then group by the record id to filter out the nulls and get the desired result. Please try this out and let me know how it goes... The number of questions in the select statements has to be equal to the number of questions of the form which has the most questions - I've put in 8 just to show you that this should not constrain you. Now you won't depend on the question name - just the sort numbering. It's good that you have the sort order - otherwise you'd have to generate a row number per each record id...

SET @rank=0; SET @id:=0; select recordid, max(qq.question1) as 'Question 1', max(qq.question2) as 'Question 2', max(qq.question3) as 'Question 3', max(qq.question4) as 'Question 4', max(qq.question5) as 'Question 5', max(qq.question6) as 'Question 6', max(qq.question7) as 'Question 7', max(qq.question8) as 'Question 8' FROM ( SELECT recordid, case when q.rownumber = 1 then CONCAT(question,': ', answer) else null end as question1, case when q.rownumber = 2 then CONCAT(question,': ', answer) else null end as question2, case when q.rownumber = 3 then CONCAT(question,': ', answer) else null end as question3, case when q.rownumber = 4 then CONCAT(question,': ', answer) else null end as question4, case when q.rownumber = 5 then CONCAT(question,': ', answer) else null end as question5, case when q.rownumber = 6 then CONCAT(question,': ', answer) else null end as question6, case when q.rownumber = 7 then CONCAT(question,': ', answer) else null end as question7, case when q.rownumber = 8 then CONCAT(question,': ', answer) else null end as question8 FROM( select recordid, question, answer, sortorder, @rank:=CASE WHEN @id=recordid THEN @rank+1 ELSE 1 END as rownumber, @id:=recordid from questions order by recordid, sortorder ) q )qq GROUP BY recordid

Upvotes: 1

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