I want to retrieve variants of the same article which are part of the same group. DBM is MySQL 5.7.
There are 2 tables:
articles
articles_group
Table articles has the fields:
article_id | title
1 first product
2 second prod
3 3rd prod
4 4th example
Table articles_groups:
group_id | article_id
1 1
1 2
1 3
2 4
In this example I would like to retrieve all other articles which are in the same group as article 1. So that would be article 2 and 3.
My best shot, but somehow pretty complex:
SELECT
art.article_id,
model
FROM
articles art
INNER JOIN
articles_group art_g ON art.article_id = art_g.article_id
WHERE art_g.group_id = (
SELECT ag.group_id
FROM articles a
INNER JOIN articles_group ag ON a.article_id = ag.article_id
WHERE a.article_id = 1
)
How can I retrieve all other articles which belong to the same group of given article in an easy way? I can still change the shema if there is a better setup.
Let's say your given article is 1. To get all articles in same group of given article, you can use subquery to get group_id of given article. Then use outer query to get all articles in same group.
SELECT a.article_id, a.title
FROM articles a
JOIN articles_groups g ON a.ref_id = g.ref_id
WHERE g.group_id = (
SELECT g.group_id
FROM articles a
JOIN articles_groups g ON a.ref_id = g.ref_id
WHERE a.article_id = '1'
)
Related
Been trying to reintroduce myself to SQL through some practice questions I've developed for myself, but struggling to find a better way of approaching the following problem:
playlists
id title
1 Title1
2 Title2
playlist_clips
id playlist_id clip_id
1 Title1 3
2 Title2 1
playlist_tags
playlist_id tag_id
1 1
1 2
2 2
Clips and Tags are two entirely separate tables, and I am using the playlist_tags and playlist_clips to connect them to the playlists table, to represent the two-way one-to-many relationships.
I wanted to select all the playlists that have a given title, and have ALL of the tags provided in the query (in this example [1, 2]), not just "at least one of them".
This is what I've come up with:
select p_clips.* from
(
select p.id, p.title, count(pc.id) as number_of_clips
from playlists p
left join playlist_clips pc on p.id = pc.playlist_id
where p.title like "Test1"
group by id
) as p_clips
inner join
(
select *
from playlists p
left join playlist_tags pt on p.id = pt.playlist_id
where pt.tag_id in (1, 2)
group by id
having count(*) = 2
) as p_tags
on p_clips.id = p_tags.id
Whilst, from my testing I've found this to work, it doesn't look particularly elegant, and I also assume it's not terribly efficient performance-wise. (I've removed irrelevant parameters from the code for this example, such as select parameters.)
What would be a cleaner way of approaching this, or at the least, a more optimized approach?
Expected Result:
id title
260 Title1
EDIT: I apologize for my initial confusing post, I've tried to clean up my tables and the information they contain.
I wanted to select all the playlists that have a given title, and have ALL of the tags provided in the query (in this example [1, 2]), not just "at least one of them".
You don't need the clips table at all. You don't need left joins or the playlists table in the subquery.
That suggests:
select p.*
from playlists p join
(select pt.playlist_id
from playlist_tags pt
where pt.tag_id in (1, 2)
group by id
having count(*) = 2
) pt
on p.id = pt.playlist_id
where p.title like 'Test1';
You could phrase this without a subquery as well:
select p.*
from playlists p join
playlist_tags pt
on p.id = pt.id
where p.title like 'Test1' and
pt.tag_id in (1, 2)
group by p.id
having count(*) = 2
I have 3 tables:
Table posts
post_id
category_id
title
Table visits
visit_id
post_id
visit_date
Table categories
category_id
category_name
I need to get something like this (assuming that table visits has 10 rows)
Category 1 (categories.category_name) / visits(count) = 5
Category 2 (categories.category_name) / visits(count) = 1
Category 3 (categories.category_name) / visits(count) = 4
How can I get a similar result using only MySQL?
I tried with INNERs, no success
It's a simple query. You need to join all three tables, and finally group the result by category name. It should look like:
select
c.category_name,
count(*)
from categories c
join posts p on p.categoryid = c.category_id
join visits v on v.post_id = p.post_id
group by c.category_name
order by c.category_name
I have simple magazine, and have tables with posts, comments, categories, etc. When listing single category, I want to have sum of comments per post in a listing, but that number is just wrong and it is driving me crazy. Note that single post can be in multiple categories.
Here are the simple tables structures
posts
id | title | categoryid | content | published
---------------------------------------------
comments
id | postid | comment
---------------------
category_rel
postid | categoryid
-------------------
categories
id | category
-------------
I use following sql (simplified to this example):
SELECT posts.*, categories.id AS categoryid,
categories.category AS categorytitle,
COUNT(comments.postid) AS CNT
FROM posts
LEFT JOIN comments ON posts.id = comments.postid
INNER JOIN category_rel ON posts.id = category_rel.postid
INNER JOIN categories ON category_rel.categoryid = categories.id
WHERE posts.published=1
GROUP BY posts.id;
This statement is giving me wrong results, sometning like it's cumulating number of categories post is member of and multiplying with actual number of comments. If I remove category part of SQL (which is not good, I need category Id and name) I receive proper values:
SELECT posts.*, COUNT(comments.postid) AS CNT
FROM posts
LEFT JOIN comments ON posts.id = comments.postid
WHERE posts.published=1
GROUP BY posts.id;
To be more specific:
One of posts have 1 comment and it is member of 7 categories. value CNT is going to 7, not 1.
Any idea how to change first SQL to get proper values?
You want to count the comments per post - not per category. So one way of achieving this would be to do the count first (in a subselect as MySQL has no CTE so far) and then join the results into category table:
SELECT countpost.*, categories.id AS categoryid,
categories.category AS categorytitle
FROM
-- subselect post and comment count
(
SELECT posts.*, count(comments.postid) as CNT FROM posts
LEFT JOIN comments ON posts.id = comments.postid
WHERE posts.published = 1
GROUP BY posts.id
) as countpost
-- join category table
INNER JOIN category_rel ON countpost.id = category_rel.postid
INNER JOIN categories ON category_rel.categoryid = categories.id ;
See this fiddle: http://sqlfiddle.com/#!9/f9c6f/1
I have a table "articles" with columns and data:
article_id title body
1 This is the title This is the body text
2 Another title Another body text
Another table "category" with columns and data:
category_id category
1 localnews
2 visible
3 first10
And a table "categories" with columns and data:
categories_id article_id category_id
1 1 1
2 1 2
3 1 3
4 2 1
5 2 3
I want to SELECT the row(s) WHERE categories.category_id = 1 AND =2 AND =3
I'm using:
SELECT articles.article_id, articles.title, articles.body,
categories.article_id, categories.category_id
FROM articles, categories
WHERE articles.article_id = categories.article_id
AND categories.article_id = 1
AND categories.article_id = 2
AND categories.article_id = 3
but it doesn't work. Obviously mySQL needs another syntax.
Can someone help?
Thanks
SELECT
Articles.article_id,
COUNT( Categories.article_id ) AS total
FROM CategoryArticles
LEFT JOIN Articles USING (article_id)
WHERE
CategoryArticles.category_id IN (1,2,3)
GROUP BY CategoryArticles.article_id
HAVING total = 3
I used a bit different names for table because in your example the distinction between category and categories is hard to notice.
An column of a row cannot be 1, 2 or 3 at the same time, which is what AND stipulates. Use OR in your WHERE condition. Better yet - for readability - you can use IN:
SELECT ...
WHERE `categories`.`article_id` IN(1,2,3)
In addition to the commonly used IN() and using a HAVING count, I would be interested in the performance difference by doing a multiple-join as follows...
SELECT STRAIGHT_JOIN
articles.article_id,
articles.title,
articles.body
FROM
categories c1
JOIN articles
on c1.article_id = articles.article_id
JOIN categories c2
on c1.article_id = c2.article_id
AND c2.category_id = 2
JOIN categories c3
on c1.article_id = c3.article_id
AND c3.category_id = 3
WHERE
c1.Category_ID = 1
Yes, this may look obscure, but lets think about it... by doing a join FIRST on the categories table where ONE of your specific categories -- THIS FIRST FROM instance of categories should be representative of whichever category would have the smallest granularity. Ex: Your categories of Local News, Visible and First 10. Local news would probably have the most entries, while Visible and First 10 would have even less... of those, which would have even the smallest number of records. Use THIS category as the where clause.
So, say you have 100,000 articles, and 90,000 are in local news, 45,000 in Visible, and 12,000 in First 10. By starting your query on only those in the 12,000, you are eliminating most of the data.
By then joining to the articles table, and categories AGAIN as alias C2 and C3 respectively based on the other conditions, if found, done, if not, its excluded.
Again, I'm wondering the performance impact. I would also have a compound index on the categories table on both (article_id, category_id)
The value cannot be all three values simultaneously, so you'd better use an IN clause in your WHERE to define which you want to return. Give you've already got a join condition there, you'd want to move that to an ON clause instead as well; ie:
SELECT articles.article_id, articles.title, articles.body, categories.article_id, categories.category_id
FROM articles
INNER JOIN categories ON articles.article_id = categories.article_id
WHERE categories.article_id IN ( 1, 2, 3 )
Of course, you can go to the next step and do:
SELECT articles.article_id, articles.title, articles.body, category.category
FROM articles
INNER JOIN categories ON articles.article_id = categories.article_id
INNER JOIN category ON categories.category_id = category.category_id
WHERE categories.article_id IN ( 1, 2, 3 )
If instead you wanted to show only articles that appear in all three categories, then you could take an approach like:
SELECT articles.article_id, articles.title, articles.body
FROM articles
INNER JOIN categories AS c1
ON articles.article_id = c1.article_id
AND c1.category_id = 1
INNER JOIN categories AS c2
ON articles.article_id = c2.article_id
AND c2.category_id = 2
INNER JOIN categories AS c3
ON articles.article_id = c3.article_id
AND c3.category_id = 3
I'm working on a mysql query in a Drupal database that pulls together users and two different cck content types. I know people ask for help with groupwise maximum queries all the time... I've done my best but I need help.
This is what I have so far:
# the artists
SELECT
users.uid,
users.name AS username,
n1.title AS artist_name
FROM users
LEFT JOIN users_roles ur
ON users.uid=ur.uid
INNER JOIN role r
ON ur.rid=r.rid
AND r.name='artist'
LEFT JOIN node n1
ON n1.uid = users.uid
AND n1.type = 'submission'
WHERE users.status = 1
ORDER BY users.name;
This gives me data that looks like:
uid username artist_name
1 foo Joe the Plumber
2 bar Jane Doe
3 baz The Tooth Fairy
Also, I've got this query:
# artwork
SELECT
n.nid,
n.uid,
a.field_order_value
FROM node n
LEFT JOIN content_type_artwork a
ON n.nid = a.nid
WHERE n.type = 'artwork'
ORDER BY n.uid, a.field_order_value;
Which gives me data like this:
nid uid field_order_value
1 1 1
2 1 3
3 1 2
4 2 NULL
5 3 1
6 3 1
Additional relevant info:
nid is the primary key for an Artwork
every Artist has one or more Artworks
valid data for field_order_value is NULL, 1, 2, 3, or 4
field_order_value is not necessarily unique per Artist - an Artist could have 4 Artworks all with field_order_value = 1.
What I want is the row with the minimum field_order_value from my second query joined with the artist information from the first query. In cases where the field_order_value is not valuable information (either because the Artist has used duplicate values among their Artworks or left that field NULL), I would like the row with the minimum nid from the second query.
The Solution
Using divide and conquer as a strategy and mysql views as a technique, and referencing this article about groupwise maximum queries, I solved my problem.
Create the View
# artists and artworks all in one table
CREATE VIEW artists_artwork AS
SELECT
users.uid,
users.name AS artist,
COALESCE(n1.title, 'Not Yet Entered') AS artist_name,
n2.nid,
a.field_image_fid,
COALESCE(a.field_order_value, 1) AS field_order_value
FROM users
LEFT JOIN users_roles ur
ON users.uid=ur.uid
INNER JOIN role r
ON ur.rid=r.rid
AND r.name='artist'
LEFT JOIN node n1
ON n1.uid = users.uid
AND n1.type = 'submission'
LEFT JOIN node n2
ON n2.uid = users.uid
AND n2.type = 'artwork'
LEFT JOIN content_type_artwork a ON n2.nid = a.nid
WHERE users.status = 1;
Query the View
SELECT
a2.uid,
a2.artist,
a2.artist_name,
a2.nid,
a2.field_image_fid,
a2.field_order_value
FROM (
SELECT
uid,
MIN(field_order_value) AS field_order_value
FROM artists_artwork
GROUP BY uid
) a1
JOIN artists_artwork a2
ON a2.nid = (
SELECT
nid
FROM artists_artwork a
WHERE a.uid = a1.uid
AND a.field_order_value = a1.field_order_value
ORDER BY
uid ASC, field_order_value ASC, nid ASC
LIMIT 1
)
ORDER BY artist;
A simple solution to this can be to create views in your database that can then be joined together. This is especially useful if you often want to see the intermediate data in the same way in some other place. While it is possible to mash together the one huge query, I just take the divide and conquer approach sometimes.