Question

How do I select a column value as a column name and group the results as a row.

I have a table as such:

id      articleId   label           value
1       1           title           Example title
2       1           description     This is the description
3       1           author          Me
4       2           title           Example of another type of article
5       2           description     Short description
6       2           author          Someone else

Is it possible to select all of the rows and use the label as the column name and the value as the value of that column name and then group them by the article name.
So how I would like to have it returned:

articleId   title           description     author
1           Example title   This is the..   Me
2           Example of an.. Short descr..   Someone else

I’m using this for a CMS where the user can define the fields for an article so we don’t have to customize the table’s. This is why i’m not making the tables as the I would like to have it returned. I am also aware that I can just as easily convert the result to this in php.

— edit —

Can this be done without knowing what labels are added? In this example im using title, description and author. But it could very well be something totally different like title, shortDescription, availableTo, techInformation, etc.. The idea is that the article’s are customizable for the user without needing to change the database and query’s

Answer 1

I figured I’d better post as an answer, even if not what OP would like to hear. What you are asking to do is to populate a query with a variable number of columns based on the distinct values within column label, all associated with articleID. Taking your specific example, the following would be the resultant query that I would most likely go to in this instance (though the example from @Devart is equally valid)

SELECT
    t.id,
    t.articleId,
    t1.value AS title,
    t2.value AS description,
    t3.value AS author

FROM `tableName` t
LEFT JOIN `tablename` t1
    ON t1.article_id = t.article_id AND t1.label = 'title'
LEFT JOIN `tablename` t2
    ON t2.article_id = t.article_id AND t2.label = 'description'
LEFT JOIN `tablename` t3
    ON t3.article_id = t.article_id AND t3.label = 'author'

Now expanding this to account for up to n labels, we get the following query (metacode included, this query will NOT execute verbatim)

SELECT DISTINCT label FROM `tableName`;

SELECT 
    t.id,
    t.articleId
    // for (i=1;i<= number of distinct labels) {
    ,t[i].value AS [value[i]]
    // }

FROM `tableName` t
// for (i=1;i<= number of distinct labels) {
LEFT JOIN `tablename` t[i]
    ON t[i].article_id = t.article_id AND t[i].label = [value[i]]
// }
;

So what you can do is one of the following.

1. SELECT t.* FROM tablename t and then have PHP process it as required
2. SELECT DISTINCT label FROM tablename and have PHP build the second query with the many LEFT JOINs (or MAX / GROUP BY logic if preferred)
3. Create a Stored Procedure to do the same as #2. This would most likely be more efficient than #2 however may be less efficient overall than #1.