Mysql - Select four rows per id in one query

Question

If I have a table of categories with a featured row that is default 0, then 1/2/3/4/5/6 to feature six categories in the order they should be displayed.

Could I use the category id from the each of the six featured to select 4 videos from the video table with corresponding categoryId's in one query and then separate the result out with foreach's?

Then return them and do foreach result as category then foreach category as videoList

SELECT id, title
FROM videos 
WHERE category = (SELECT id FROM category WHERE featured > 0) 
LIMIT 4

to return something like this:

foreach($result as $categoryVideos):
    echo $categoryVideos[categoryName];
    foreach($categoryVideos as $video):
        echo $video[title];
    endforeach;
endforeach;

I know it needs joins etc but am I making this way too complicated? I'm blaming my blank mind on a lack of sleep as I'd usually be the one answered a question like this ..

It's more complicated because I'm trying to pass all this data from a model to the controller in one go as $result?

score 2 · Answer 1 · answered Mar 30 '12 at 02:43

2

Your basic approach will work, but you have a few problems with your SQL:

LIMIT 4 will not necessarily return records in the order you expect. Use ORDERBY to tell SQL what order you want the records in. If I understand correctly the category ranking is in the category table. If that's the case, you need ORDERBY and the limit in the subquery, e.g. SELECT id FROM category WHERE featured > 0 ORDERBY featured LIMIT 4.
Your subquery WHERE category = (SELECT... syntax is wrong. Replace = with IN.

answered Mar 30 '12 at 02:43

Eric J.

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I think OP is trying to retrieve 24 rows, 4 from each of 6 categories. – kijin Mar 30 '12 at 03:04
Yes that's correct, at the moment I can get 1 from each but not 4 from each? – Dan Mar 30 '12 at 03:41

score 1 · Accepted Answer · edited May 23 '17 at 12:11

1

You're trying to fetch 4 rows from each of 6 categories, right? For a total of 24 rows?

The first answer to this question is probably applicable to your case.

edited May 23 '17 at 12:11

Community

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answered Mar 30 '12 at 03:11

kijin

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Mysql - Select four rows per id in one query

2 Answers2