I'm trying to select all posts from a specific category along with some additional data from another table.
Despite my efforts none of the sql queries that I've tried have worked out so far.
Here is my code.
SELECT
a.*,
b.*
FROM forum_posts AS a
LEFT JOIN forum_categories AS b ON a.post_category = b.category_id
WHERE category_slug = 'news-and-anouncements'
Here's a screenshot to illustrate the result I'm trying to achieve.
As you can see I'm grabbing posts from the posts table, but I also wish to get the category fields without re-selecting them in each post selection, if that makes sense.
Any ideas on how I should tweak the query?
Related
I’ve been creating a database called news which contains few tables with different information in them, articles employees, pictures etc. There is two things which I’m trying to do, first is to get the three most commented articles and they need to be in order with the one with most comments first.
This is the code that I’ve got which I’ve been working on. I have a table named comments which contains article ID etc.
SELECT a.ArticelID, a.preamble, a.Published, k.postcount FROM Article as a
INNER JOIN (
SELECT ArticelID,
count(*) AS postcount
FROM comments
GROUP BY ArticelID
) as k
on a.ArticelID = k.ArticelID
ORDER by k.postcount DESC LIMIT 3
But it feels kind of unineffective I would only like to simply use a Join and Group By but I can’t get it through my head how it is supposed to look.
The last thing I want to do is get relevant information from an article when it comes to what pictures the article has. I have two tables, one articles and one that is pictures, what I got so far is
SELECT PictureID, Filname, photographerName, ArticelID
FROM PictureID, Articel_Picture
WHERE PictureID IN (2);
But I keep on getting error that says “Column PictureID is ambiguous” how am I supposed to handle that message?
Your first query is fine, but you can also phrase it as:
SELECT a.ArticelID, a.preamble, a.Published, count(*) as CommentCount
FROM Article a join
comments c
on a.ArticleId = c.ArticleId
ORDER by CommentCount DESC
LIMIT 3;
For the second query, you need a join and aliases:
SELECT p.PictureID, p.Filname, p.photographerName, ap.ArticelID
FROM PictureID p join
Articel_Picture ap
on p.PictureId = ap.PictureId
WHERE ap.PictureID IN (2);
I'm having some problems with a query I'm writing. This seems like table structure that is very frequent so I'd love some help.
Let's say I have 3 tables similar to a facebook structure. Users, Wall Posts, and Comments. Users can make wall posts, and comment on other wall posts.
On a users page I would like to show a users wall posts and a count of how many comments that post has. This is what I have so far
I query the Wall Post table using the users id as an inner join to the User table. That gives me a result set of wall posts for that user's page. Then I loop through that result set, take the Wall Post id from each result set, and query the Comment table for the Count of comments for that Wall Post Id. This works, however I have to hit the db twice. Can anyone think of a way that I could do this with one query?
First Query Example:
SELECT wallPost.*, user.currentDefault, user.displayName, user.userName
FROM wallPost
INNER JOIN user ON user.id = wallPost.sourceUserId
WHERE wallPost.recipientId = ? ORDER BY wallPost.id DESC
Second Query Example:
SELECT COUNT(id) AS count
FROM comment
WHERE wallPostId = ?
I would add the count as a subquery and join the subquery to the main query
SELECT
wallPost.*,
user.currentDefault,
user.displayName,
user.userName,
wallpost_commentcount.total
FROM
wallPost
INNER JOIN user ON user.id=wallPost.sourceUserId
LEFT JOIN (SELECT wallPostId,COUNT(*) as total FROM comment GROUP BY wallPostId) as wallpost_commentcount ON (wallpost_commentcount.wallPostId=wallPost.id)
WHERE
wallPost.recipientId = ?
ORDER BY wallPost.id DESC
Please make sure you have an index on comment.wallPostId otherwise this query will take a long time.
I used the LEFT JOIN because you always want to get the wallPost even if there are no comments records yet
There are 4 sql tables:
Listings(Amount, GroupKey, Key, MemberKey),
Loans(Amount, GroupKey, Key, ListingKey),
Members(City, GroupKey, Key)
Groups(GroupRank, Key, MemberKey)
Now, if one wants to find out the loans which are also listings and find the members city and GroupRank for the members in the loan table. Here, the group table contains information about grous of which members are a part of.
and also perform a select operation as given below:
select Listings.Amount, Members.City, Groups.GroupRank
from listings, loans, members, groups
where Listings.Key=Loans.ListingKey and
Members.Key=Listings.MemberKey and
Listings.GroupKey=Groups.Key
The above join is giving an incorrect result, please point out where I am going wrong.
Also I am new to SQL so please excuse the novice question.
Note: The following is just a guess what your problem is. Like others said, clearify your question.
You want to JOIN
( http://dev.mysql.com/doc/refman/5.1/de/join.html )
those tables. What you write is just another form of a join, meaning it has the same effect. But you "joined" a bit too much. To make things clearer a syntax has been invented to make things clearer and avoid such mistakes. Read more about it in the link given above.
What you want to achieve can be done like this:
SELECT
Listings.Amount, Members.City, Groups.GroupRank
FROM
Listings
INNER JOIN Groups ON Listings.GroupKey=Groups.Key
INNER JOIN Members ON Members.Key=Listings.MemberKey
You don't do a SELECT on the Loans table, you don't need it in this query.
This is the INNER JOIN which will give you a result where every row in table A has an according entry in table B. When this is not the case, you have to use the LEFT or RIGHT JOIN.
Maybe the problem is related to the join type (INNER). Try LEFT JOIN for example but Mark has right: you should clearify your question.
I would firstly change your query to use the more modern join syntax, which allows outer joins. Tr this:
select Listings.Amount, Members.City, Groups.GroupRank
from listings
left join loans on Listings.Key=Loans.ListingKey
left join members on Members.Key=Listings.MemberKey
left join groups on Listings.GroupKey=Groups.Key
and/or Loans.GroupKey=Groups.Key
and/or Members.Key=Groups.MemberKey
You may need to play with the criteria on the last join (maybe they should be "or" not "and" etc).
I am trying to build a sql query that I think it involves inner joins, but I can't figure it out. Here's the model:
There's two tables: comments, posts
Among many columns, there's the following important ones: comments.id, comments.user_id (owner), comments.post_id (reference to posts table), posts.id, posts.editor_id (which is the person, ie, owner of post).
I want to get the comments that either
1) current user has written, so something like:
select * from comments where user_id = <<current_user_id>>
2) (Assume current_user is editor). Get all comments that belong to a post that you have created.
This is what I have, but I get multiple lines....what am I missing?
select * FROM comments INNER JOIN posts ON comments.post_id = <<test_id>>
WHERE posts.editor_id = <<current_user.editor_id>>;
If you could give me a sql query that includes both of these things, that would be amazing.
Thanks!
Im not sure what you mean by "multiple lines" as you would return a row for each comment.
This should do it.
SELECT comments.*
FROM comments
INNER JOIN posts
ON comments.post_id = posts.id
WHERE posts.editor_id = #editorID;
I want to get the comments that either 1) current user has written, so something like: select * from comments where user_id = <>
That's correct. What's wrong with that?
Get all comments that belong to a post that you have created. This is what I have, but I get multiple lines
Well... you're supposed to. Looking at the schema it's indeed a post could contain many comments. The query given by tyrongower should do what you want.
Going with your requirements, this should work for you:
SELECT * FROM comments
WHERE (user_id = 1)
OR (post_id IN (SELECT id FROM post WHERE editor_id = 1))
In the above query "1" is used as a sample and should be replace with the id of current user.
I am using this query to print out a forum board and all it's sub forums. What happens, as may be expected, is that all posts in all threads belonging to that forum are displayed. What I would like to happen is only the first post from each thread is displayed along with the forum title.
Query:
SELECT tf_threads.*, tf_posts.*
FROM tf_threads INNER JOIN tf_posts
ON tf_threads.thread_id=tf_posts.thread_id
AND tf_threads.parent_id=54 ORDER BY tf_posts.date ASC
Please note the parent_id field is given a variable in the real query.
So. If I make sense, can anyone help me out as to what query to write to only select the first post from each thread?
If there are no simple(ish) answers, how could I do it if I used a post number field in the second table, for example, the first post in thread has number 1, second post has number 2, etc. If I use this method, I'd obviously only like to select posts with a count number field of 1. I could just expand the original query with a AND post_number=1 right?
Thanks for reading,
James
Something like this?
http://murrayhopkins.wordpress.com/2008/10/28/mysql-left-join-on-last-or-first-record-in-the-right-table/
Edit: I think that it has to be something like this, but I'm also not an SQL expert:
SELECT tf_threads.*, tf_posts_tmp.*
FROM tf_threads
LEFT JOIN (SELECT p1.*
FROM tf_posts as p1
LEFT JOIN tf_posts AS p2
ON p1.postid = p2.postid AND p1.date < p2.date) as tf_posts_tmp
ON (tf_threads.thread_id=tf_posts_tmp.thread_id)