Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

MySQL query output columns from rows

Posted on 2014-03-03
5
Medium Priority
?
665 Views
Last Modified: 2014-03-04
I want to query a table called Vote_Record and output row data in columns, as follows:

Table: Vote_Record
+-------+---------+--------+
| Name	| Issue| Vote	|
+-------+---------+--------+
| Tom	| A	|  Yes	|
| Dick	| A	|  No	|
| Harry	| A	|  No	|
| Tom	| B	|  Yes	|
| Dick	| B	|  Yes	|
| Harry	| B	|  No	|
| Tom	| C	|  Yes	|
| Dick	| C	|  Yes	|
| Harry	| C	|  Yes	|
+-------+---------+--------+

Query Output
+---------+--------------+--------------+-------------+
| Name	| Issue A	| Issue B      | Issue C   |
+---------+--------------+--------------+-------------+
| Tom      | Yes        | Yes            | Yes           |
| Harry	| No         | No             | Yes          |
+---------+--------------+--------------+-------------+

Open in new window


Sorry for the crazy table formatting -- I couldn't figure out how line up the columns...

Thanks!
0
Comment
Question by:Ron1959
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
5 Comments
 
LVL 17

Expert Comment

by:Kent Dyer
ID: 39902575
Baiscally, you are looking to do a PIVOT Query..

something like this..

select t3.name, t3.Issue_A, t3.Issue_B, t3.Issue_C  
from
(select t2.name as name, 
case when Issue_1 then "Yes"
else "No" end  Issue_A, 

case when Issue_2 then "Yes"
else "No" end Issue_B,

case when Issue_3 then 'Yes"
else "No" end Issue_C

from 
(SELECT partners.name as name, sales.products_id as prodid, count(products.name) as counts
FROM test.sales left outer join test.partners on sales.partners_id = partners.id
left outer join test.products on sales.products_id = products.id 
where sales.partners_id = partners.id and sales.products_id = products.id group by partners.name, prodid) t2) t3

group by t3.name ;

Open in new window

0
 
LVL 59

Accepted Solution

by:
Julian Hansen earned 2000 total points
ID: 39902707
Assuming you have only 3 issue types then you can use the following query - if you have more then extend to match
SELECT `name`, 
	MAX(CASE WHEN issue='A' THEN vote END) IssueA, 
	MAX(CASE WHEN issue='B' THEN vote END) IssueB, 
	MAX(CASE WHEN issue='C' THEN vote END) IssueC
FROM `table`
GROUP BY `name`;

Open in new window

0
 

Author Closing Comment

by:Ron1959
ID: 39903175
Wow, that's a very clean solution.  It should be easy to manage a large number of issues.

Please watch for my next question, which will have to do with "weighting" the votes and summing them for a total score.

Thanks!
0
 
LVL 59

Expert Comment

by:Julian Hansen
ID: 39903184
You are welcome - thanks for the points.
0
 
LVL 111

Expert Comment

by:Ray Paseur
ID: 39903201
Matrix inversion is a standard computer science problem, and there are many ways to do it.  This demonstrates the PHP logic.  

The essential moving parts look something like this (note the position of rows and columns in these two examples).

// CREATE THE EMPTY MATRIX OF COLUMNS (NAMES) AND ROWS (QUESTIONS)
$mat = array();
foreach ($cols as $c)
{
    foreach ($rows as $r)
    {
        $mat[$c][$r] = '-';
    }
}

Open in new window

// CREATE THE EMPTY MATRIX OF COLUMNS (QUESTIONS) AND ROWS (NAMES)
$mat = array();
foreach ($rows as $r)
{
    foreach ($cols as $c)
    {
        $mat[$r][$c] = '-';
    }
}

Open in new window

0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This post looks at MongoDB and MySQL, and covers high-level MongoDB strengths, weaknesses, features, and uses from the perspective of an SQL user.
In this article, we’ll look at how to deploy ProxySQL.
The viewer will learn how to dynamically set the form action using jQuery.
In this video, Percona Solutions Engineer Barrett Chambers discusses some of the basic syntax differences between MySQL and MongoDB. To learn more check out our webinar on MongoDB administration for MySQL DBA: https://www.percona.com/resources/we…
Suggested Courses

618 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question