Kind people of Stackoverflow, I am currently struggling with a small part of my latest project.
Currently working with an image gallery.
For simplicity, I have two tables:
**albums**
album_id, album_title
**media**
media_id, album_id, media_title
I need to display a list of 5 albums and for each album up to 5 items of media in that album.
So I want my query to select 5 albums, and then up to 5 media items that have the same album_id
I want to perform this with the minimum number of queries possible, and also the best performance as possible (so I have this working already by just getting all albums, getting all media and then looping through them, but that isn't scalable if some albums contain hundreds of media items).
I always appreciate the fantastic help I get here. Thank you.
You can get the media in a comma delimited list by using group_concat()
:
select a.*,
substring_index(group_concat(distinct m.media_title), ',', 5)
from albums a join
media m
on a.album_id = m.album_id
group by a.album_id
limit 5;
By way of example...
CREATE TABLE colours(colour_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,colour VARCHAR(20) NOT NULL);
INSERT INTO colours VALUES (1,'red'),(2,'orange'),(3,'yellow'),(4,'green'),(5,'blue'),(6,'indigo'),(7,'violet');
CREATE TABLE things
(thing VARCHAR(20) NOT NULL PRIMARY KEY,colour VARCHAR(20));
INSERT INTO things VALUES
('tomato','red'),
('cherry','red'),
('heart','red'),
('ferrari','red'),
('chrysanthemum','orange'),
('orange','orange'),
('banana','yellow'),
('lemon','yellow'),
('sunflower','yellow'),
('caterpillar','green'),
('cucumber','green'),
('grass','green'),
('sky','blue'),
('suede shoes','blue'),
('bluebell','blue'),
('indigo bunting','indigo'),
('violets','violet');
SELECT c.colour
, y.thing
FROM colours c
JOIN things x
ON x.colour = c.colour
JOIN things y
ON y.colour = x.colour
AND y.thing <= x.thing
WHERE c.colour_id <=3
GROUP
BY c.colour,x.thing
HAVING COUNT(*) <=3
ORDER
BY colour_id;
+--------+---------------+
| colour | thing |
+--------+---------------+
| red | cherry |
| red | cherry |
| red | cherry |
| orange | chrysanthemum |
| orange | chrysanthemum |
| yellow | banana |
| yellow | banana |
| yellow | banana |
+--------+---------------+
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