I have this database format below (taken from phpmyadmin, the tables are relational already):
I'm trying to get all "videos.Video_Name, videos.Video_URL" with a certain "tags.Tag_Name" via the "tagmap" relational mapping. I've never really used MySQL before for anything more than SELECT's and DELETE's and the syntax of JOIN is proving too much to bear, and at this point it'd just be faster to ask for help than to keep bashing my head against it.
I know I should be using JOIN but I have no idea of the syntax to accomplish what I want.
The completely invalid query I tried was:
SELECT videos.Video_URL, videos.Video_Name
FROM tagmap
INNER JOIN videos ON videos.Video_ID = tagmap.Video_ID
INNER JOIN tagmap ON tagmap.Tag_ID = tags.Tag_ID
WHERE tags.Tag_Name = '$_GET[tag]'
But it returned no rows.
If your query returned no raws and did not a return an error then it's not "completely invalid".
Indeed, looking at the code, it should do exactly what you say you are trying to achieve. Hence if it's returning no rows then the reason must be that there is no matching data.
Break it down to find out where the data is missing:
SELECT COUNT(*)
FROM tags
WHERE tags.Tag_Name = '$_GET[tag]';
If you get a non-zero value then try....
SELECT COUNT(DISTINCT tagmap.Video_ID), COUNT(*)
FROM tags INNER JOIN tagmp
ON tags.tag_ID=tagmap.tag_ID
WHERE tags.Tag_Name = '$_GET[tag]';
(BTW you might want to read up on SQL Injection).
Now Try this one.
SELECT videos.Video_Name, videos.Video_URL FROM videos,tags,tagmap
WHERE videos.Video_ID = tagmap.Video_ID AND tags.Tag_ID = tagmap.Tag_ID AND
tags.Tag_Name='$_GET[tag]'
Same Result with Joins
SELECT videos.Video_Name, videos.Video_URL FROM tagmap
RIGHT JOIN videos ON videos.Video_ID = tagmap.Video_ID
LEFT JOIN tags ON tags.Tag_ID = tagmap.Tag_ID
WHERE tags.Tag_Name = '$_GET[tag]'
Hope it will not give any error.
Thanks.
Related
I'm facing a problem here:
I'm building a forum, this forum has several tables and I'm trying to fetch the comments and user info in a single query.
So far, it should be easy, the problem is that I can't change the structure and with the following query I get a perfect result IF there is a like to the answer. If no one likes the answer it fails.
Select
mfr.mfr_forum_answers.id,
mfr.mfr_forum_answers.date_created,
mfr.mfr_forum_answers.last_updated,
mfr.mfr_forum_answers.content,
mfr.mfr_forum_answers.accepted,
mfr.mfr_forum_answers.user_id,
mfr.mfr_users.level,
mfr.mfr_users.avatar,
mfr.mfr_forum_likes.subject_id,
mfr.wp_users.ID As ID1,
mfr.mfr_forum_topics.user_id As owner_id,
(SELECT count(mfr.mfr_forum_likes.id) FROM mfr.mfr_forum_likes WHERE mfr.mfr_forum_likes.subject_id = :id AND mfr.mfr_forum_likes.type = 'answer') as likes,
(SELECT count(mfr.mfr_forum_likes.id) FROM mfr.mfr_forum_likes WHERE mfr.mfr_forum_likes.subject_id = :id AND makefitreal.mfr_forum_likes.type = 'answer' AND mfr.mfr_forum_likes.user_id = :sessionId ) as i_like,
mfr.wp_users.user_nicename
From
mfr.mfr_forum_likes Inner Join
mfr.mfr_forum_answers
On mfr.mfr_forum_answers.topic_id =
mfr.mfr_forum_likes.subject_id Inner Join
mfr.mfr_users
On mfr.mfr_forum_answers.user_id = mfr.mfr_users.id
Inner Join
mfr.wp_users
On mfr.mfr_users.id = mfr.wp_users.ID Inner Join
mfr.mfr_forum_topics
On mfr.mfr_forum_answers.topic_id = mfr.mfr_forum_topics.id
Where
mfr.mfr_forum_answers.topic_id = :id
And
mfr.mfr_forum_likes.type = 'answer'
So far as said it returns only if an answer has a like, I'm thinking on adding a add to the user who posts the answer by default but I'm trying to improve my skills by solving new issues.
If someone has a suggestion in how I could overcome the fact that if a table is empty, the query continues I'd be really thankfull.
Thanks in advance-
Pihh
Yes. What you are looking for are called left and right joins. According to the documentation, with a LEFT JOIN you still join two tables as normal but
If there is no matching row for the right table in the ON or USING part in a LEFT JOIN, a row with all columns set to NULL is used for the right table.
This means that you can try to join two tables, but if a row does not have any results it will still return the results from the first table. The same is true for a RIGHT JOIN only it works the opposite way: it will return results if the tabled being joined to has results, but the original table does not.
It looks like you have 3 tables for 3 relationships: there are answers, a user gives an answer, and an answer might or might not have like. To grab this data, I would suggest starting from your answers table, performing an INNER JOIN on your users table (assuming there are always users), and a LEFT JOIN on your likes table. Here is a simple example:
SELECT *
FROM answers
INNER JOIN users ON users.id = answers.user_id
LEFT JOIN likes ON likes.answer_id = answer.id
WHERE answers.id = :id
AND likes.type = 'answers'
Of course, if for some unknown reason you need to start from your likes table, then you'd have to RIGHT JOIN the other tables. I hope that gives you a good idea of how you'd make your query.
Can someone please help me in writing the exact query, which can give me desired results for the following,
I wrote,
SELECT tbl_order_detail.order_id,
tbl_order_detail.order_title,
tbl_order_detail.dealer_id
FROM tbl_order_detail
LEFT JOIN tbl_order_lead_send_detail ON tbl_order_detail.order_id=tbl_order_lead_send_detail.order_id
WHERE tbl_order_detail.order_status = 'Active'
and finding the dealer name from one php function that takes dealer_id in it and returns dealer_name (using another mysql query), and count from another mysql query
but it isn't giving my desired output. it's giving output as
But I want the above circled ones in one row only, as everything is same in them, but they are showing many times in the output (why not one).
Can someone help me in this?
If you GROUP BY order_id, you should be good to go
Edit:
To get the dealer name, just JOIN the dealer table and select the dealer name column.
Untested, may contain errors
SELECT
tbl_order_detail.order_id,
tbl_order_detail.order_title,
dealer.dealer_name,
COUNT(tbl_order_lead_send_detail.order_id) AS total_customers_count
FROM tbl_order_detail
JOIN dealers ON (tbl_order_detail.dealer_id = dealers.dealer_id)
LEFT JOIN tbl_order_lead_send_detail ON (tbl_order_detail.order_id = tbl_order_lead_send_detail.order_id)
WHERE tbl_order_detail.order_status = 'Active'
GROUP BY tbl_order_detail.order_id, tbl_order_detail.order_title, dealer.dealer_name;
To get a count, use COUNT(). To group your results by Order ID, use GROUP BY tbl_order_detail.order_id - one of the upsides of MySQL (or SQL in general) is that it's fairly close to plain English.
Try this:
SELECT OD.order_id,
OD.order_title,
OD.dealer_id,
SD.customer_id,
COUNT(SD.id) AS NumCustomers
FROM tbl_order_detail OD
LEFT JOIN tbl_order_lead_send_detail SD
ON OD.order_id=SD.order_id
WHERE OD.order_status='Active'
GROUP BY OD.order_id,
OD.order_title,
OD.dealer_id,
SD.customer_id
So I've got a little forum I'm trying to get data for, there are 4 tables, forum, forum_posts, forum_threads and users. What i'm trying to do is to get the latest post for each forum and giving the user a sneak peek of that post, i want to get the number of posts and number of threads in each forum aswell. Also, i want to do this in one query. So here's what i came up with:
SELECT lfx_forum_posts.*, lfx_forum.*, COUNT(lfx_forum_posts.pid) as posts_count,
lfx_users.username,
lfx_users.uid,
lfx_forum_threads.tid, lfx_forum_threads.parent_forum as t_parent,
lfx_forum_threads.text as t_text, COUNT(lfx_forum_threads.tid) as thread_count
FROM
lfx_forum
LEFT JOIN
(lfx_forum_threads
INNER JOIN
(lfx_forum_posts
INNER JOIN lfx_users
ON lfx_users.uid = lfx_forum_posts.author)
ON lfx_forum_threads.tid = lfx_forum_posts.parent_thread AND lfx_forum_posts.pid =
(SELECT MAX(lfx_forum_posts.pid)
FROM lfx_forum_posts
WHERE lfx_forum_posts.parent_forum = lfx_forum.fid
GROUP BY lfx_forum_posts.parent_forum)
)
ON lfx_forum.fid = lfx_forum_posts.parent_forum
GROUP BY lfx_forum.fid
ORDER BY lfx_forum.fid ASC
This get the latest post in each forum and gives me a sneakpeek of it, the problem is that
lfx_forum_posts.pid =
(SELECT MAX(lfx_forum_posts.pid)
FROM lfx_forum_posts
WHERE lfx_forum_posts.parent_forum = lfx_forum.fid
GROUP BY lfx_forum_posts.parent_forum)
Makes my COUNT(lfx_forum_posts.pid) go to one (aswell as the COUNT(lfx_forum_threads.tid) which isn't how i would like it to work. My question is: is there some somewhat easy way to make it show the correct number and at the same time fetch the correct post info (the latest one that is)?
If something is unclear please tell and i'll try to explain my issue further, it's my first time posting something here.
Hard to get an overview of the structure of your tables with only one big query like that.
Have you considered making a view to make it easier and faster to run the query?
Why do you have to keep it in one query? Personally I find that you can often gain both performance and code-readability by splitting overly complicated queries into more parts.
But hard to get an overview so can't really give a good answer to your question:)
Just add num_posts column to your table. Don't count posts with COUNT().
Can we get some...
Show Tables;
Desc Table lfx_forum_posts;
Desc Table lfx_forum_threads;
Desc Table lfx_forum_users;
Desc Table lfx_forum;
Here's some pseudo code
select f.*, (select count(*) from forum_posts fp where fp.forum_id = f.id) as num_posts,
(select count(*) from forum_threads ft where ft.forum_id = f.id) as num_threads,
(select max(fp.id) from forum_posts fp
where fp.id = f.id
) as latest_post_id,
from forums f;
Then go on to use latest_post_id in a seperate query to get it's information.
if it doesn't like using f before it's declared then make a temporary table for this then you update every time the query is ran.
What I want to do is get the data from two different tables (table1 and table2) where row1 = 'test' in both of the tables
You'll want to use an INNER JOIN here - something along these lines (can't tell you for sure since you didn't give the structure of your tables)...
SELECT * FROM thread t
INNER JOIN post_display pd ON pd.threadid = t.threadid
WHERE t.threadid = 2
ORDER BY t.threadid DESC
Note: SELECT * can be very bad if you're selecting a bunch of fields you're never going to need. Once you have the query working, narrow down your select to the specific fields you're looking to work with.
More info on JOIN syntax for MySQL is available here: http://dev.mysql.com/doc/refman/5.1/en/join.html
I'm not quite sure what you're asking, but if you want to fetch columns from multiple tables at once (and it sounds like you're saying rows when you mean columns) you probably want a JOIN, which is an SQL feature
I am not getting what you are asking about.. but.. i can give u suggestion on you asked question.. u can try this.. have a look
SELECT * FROM table1 t1
INNER JOIN table2 t2 ON t1.id = t2.t1id
WHERE t1.row1 like 'test' AND t2.row like 'row';
This is the query. Im mostly interested if there is a better way to grab the stuff I use GROUP_CONCAT for, or if thats a fairy good way of grabbing this data. I then explode it, and put the ids/names into an array, and then use a for loop to echo them out.
SELECT
mov_id,
mov_title,
GROUP_CONCAT(DISTINCT categories.cat_name) as all_genres,
GROUP_CONCAT(DISTINCT cat_id) as all_genres_ids,
GROUP_CONCAT(DISTINCT case when gen_dominant = 1 then gen_catid else 0 end) as dominant_genre_ids,
GROUP_CONCAT(DISTINCT actors.act_name) as all_actors,
GROUP_CONCAT(DISTINCT actors.act_id) as all_actor_ids,
mov_desc,
mov_added,
mov_thumb,
mov_hits,
mov_numvotes,
mov_totalvote,
mov_imdb,
mov_release,
mov_html,
mov_type,
mov_buytickets,
ep_summary,
ep_airdate,
ep_id,
ep_hits,
ep_totalNs,
ep_totalRs,
mov_rating,
mov_rating_reason,
mrate_name,
dir_id,
dir_name
FROM movies
LEFT JOIN _genres
ON movies.mov_id = _genres.gen_movieid
LEFT JOIN categories
ON _genres.gen_catid = categories.cat_id
LEFT JOIN _actors
ON (movies.mov_id = _actors.ac_movid)
LEFT JOIN actors
ON (_actors.ac_actorid = actors.act_id AND act_famous = 1)
LEFT JOIN directors
ON movies.mov_director = directors.dir_id
LEFT JOIN movie_ratings
ON movies.mov_rating = movie_ratings.mrate_id
LEFT JOIN episodes
ON mov_id = ep_showid AND ep_season = 0 AND ep_num = 0
WHERE mov_id = *MOVIE_ID* AND mov_status = 1
GROUP BY mov_id
EXPLAIN of the query is here
alt text http://www.krayvee.com/o2/explain.gif
Personally, I would try to break the query up into multiple queries. Mostly I would recommend removing the Actor and Genre Joins so that you can get rid of all those group_concat functions. Then do separate queries to pull this data out. Not sure if it would speed things up, but it's probably worth a shot.
You've basically done a Cartesian product between genres, actors, directors, movie_ratings and episodes. That's why you have to use DISTINCT inside your GROUP_CONCAT(), because the pre-grouped result set has a number of rows equal to the product of the number of matching rows in each related table.
Note that this query wouldn't work at all in SQL, except that you're using MySQL which is permissive about the single-value rule.
Like #Kibbee, I usually recommend to run separate queries in cases like this. It's not always better to run a single query. Try breaking up the query and doing some profiling to be sure.
PS: What? No _directors table? So you can't represent a move with more than one director? :-)