LEFT JOIN 3 columns to get username - mysql

I have three columns I need to join which comes from 3 different tables,
Contributions table:
+-----------+---------------------+
| record_id | contributor_user_id |
+-----------+---------------------+
| 1 | 2 |
+-----------+---------------------+
| 1 | 5 |
+-----------+---------------------+
Members table:
+--------------+---------+
| username | user_id |
+--------------+---------+
| Test | 1 |
+--------------+---------+
| Test2 | 5 |
+--------------+---------+
| Test3 | 6 |
+--------------+---------+
Records table:
+---------+-----------+
| user_id | record_id |
+---------+-----------+
| 28 | 1 |
+---------+-----------+
For what I need to return is the username and user_id for displaying the record owner. Also, display the username and the user_id, but this can be multiple (more than 1+ user). I've tried this:
SELECT usr.username,
usr.user_id,
rec.record_id,
contrib.record_id,
contrib.contributor_user_id
FROM
(
records rec
INNER JOIN members usr ON rec.user_id = usr.user_id
# this returns records as NULL
LEFT OUTER JOIN contributions contrib ON rec.record_id = contrib.record_id AND contrib.contributor_user_id = usr.user_id
# this works, but I need the username to be displayed too
LEFT OUTER JOIN contributions contrib ON rec.record_id = contrib.record_id
)
WHERE rec.record_id = 1

Try nesting the join for contributing users inside of the left join to contributions.
SELECT u.username, u.user_id, r.record_id, u2.username as ContributorName, u2.user_id as ContributorId
FROM records r
INNER JOIN members u
ON r.user_id = u.user_id
LEFT JOIN contributions c
INNER JOIN members u2
ON c.contributor_user_id = u2.user_id
ON r.record_id = c.record_id
WHERE r.record_id = 1

SELECT
usr.username AS record_owner
, usr.user_id AS record_owner_id
, rec.record_id
, con.contributor_user_id AS contributor_id
, contributors.username AS contributor_name
FROM
records rec
INNER JOIN
members usr
ON rec.user_id = usr.user_id
LEFT OUTER JOIN
contributions con
ON rec.record_id = con.record_id
INNER JOIN
members contributors
ON con.contributor_user_id = contributors.user_id
WHERE
rec.record_id = 1

Related

Many to Many relationships with an initial pivot condition

I have three tables groups, users and group_user.
While groups and users have an id and name column, the bellow is
the group_user table
+----+----------+---------+
| id | group_id | user_id |
+----+----------+---------+
| 12 | 5 | 1 |
| 13 | 5 | 8 |
| 14 | 5 | 7 |
+----+----------+---------+
The issue am facing is, I have a user with id 7, and am trying
to get the group of this user (which is 5 from above schema diagram), then retrieve every other user
in that group (user with id 1 and 8).
I tried doing something like this:
select `groups`.id, `groups`.name, users.id, users.name from `groups`
left join group_user on `groups`.id = group_user.group_id and group_user.user_id = 7
left join users on group_user.user_id = users.id
And expectedly the result is not accurate
Please try following query:
select g.name group_name, u.name user_name from group_user gu
left join users u on u.id = gu.user_id
left join groups g on g.id = gu.group_id
where gu.group_id in (select group_id from group_user where user_id = 7)
You must join users to 2 copies of group_user and finally groups with INNER joins:
select gu2.group_id, g.name group_name, u.id user_id, u.name user_name
from `users` u
inner join group_user gu on gu.user_id = u.id
inner join group_user gu2 on gu2.group_id = gu.group_id and gu2.user_id = 7
inner join `groups` g on g.id = gu2.group_id
See a simplified demo.

join pivot table in mysql

How to join different tables with pivote table
I have 4 tables like
users
id | name |
-------------
1 | abc |
2 | ccc |
user_profile
id | user_id | email |
-------------------------------
1 | 1 | abc#gmail.com
2 | 2 | ccc#gmail.com
skills
id | skill_name |
--------------------------
1 | java |
2 | php |
user_skills
user_id | skill_id |
---------------------------
1 | 1 |
1 | 2 |
2 | 1 |
The result should be
name | email | skills |
----------------------------------
abc |abc#gmail.com | java, php |
ccc |ccc#gmail.com | java |
I am able to join multiple tables but I have problem joining pivote
I have tried below with query
SELECT users.name,user_profiles.email, group_concat(programs.name)
from users
JOIN user_profiles on user_profiles.user_id = users.id
LEFT JOIN user_skills on user_skills.user_id = users.id
LEFT JOIN skills on user_skills.skill_id = skills.id
GROUP BY users.id
Can anyone help me on this please??Thanks
You need GROUP_CONCAT to generate the CSV list of skills:
SELECT
u.name,
up.email,
GROUP_CONCAT(s.skill_name) AS skills
FROM users u
INNER JOIN user_profile up
ON u.id = up.user_id
LEFT JOIN user_skills us
ON u.id = us.user_id
INNER JOIN skills s
ON us.skill_id = s.id
GROUP BY
u.id, u.name, up.email;
Demo
Note that I group by both the user's id and name, because perhaps two users happen to have the same name. Follow the link below for a running SQLFiddle.
Your query should work. Perhaps the problem is the reference to programs rather than skills:
select u.name, up.email, group_concat(s.name)
from users u join
user_profiles up
on up.user_id = u.id left join
user_skills us
on us.user_id = u.id left join
skills s
on us.skill_id = s.id
group by u.name, up.email;

Multiple joins with multiple conditions with multiple tables

at first my tables:
game
+----+--------------+
| id | game |
+----+--------------+
| 1 | Game1 |
| 2 | Game2 |
| 4 | Game4 |
+----+--------------+
group_game
+---------+----------+
| game_id | group_id |
+---------+----------+
| 1 | 33 |
| 1 | 45 |
| 4 | 33 |
+---------+----------+
groups
+----+------------+----
| id | group_name | ...
+----+------------+----
| 33 | Group33 | ...
| 45 | Group45 | ...
+----+------------+----
users
+---------+----------+----
| user_id | username | ...
+---------+----------+----
| 1 | User1 | ...
| 2 | User2 | ...
+---------+----------+----
users_groups
+---------+----------+
| user_id | group_id |
+---------+----------+
| 1 | 33 |
| 1 | 45 |
| 2 | 45 |
+---------+----------+
What I want to do
Now I want to check wether the current user is in a group which plays "Game4" and if yes the output should be the id and the name of the group.
the current user is "User1" with the ID 1 (table users)
"User1" is in a group with the ID 33 (table users_groups)
The Group-ID 33 belongs to "Group33" (table groups)
The Group with the ID 33 plays the Game with the ID 4 (table group_game)
The Game with the ID belongs to the game "Game4" (table game)
CONCLUSION: Yes, the user is in a group which plays Game4, so output the name of the group ("Group33")
My current code for that (which gives me no rows)
$user_id = $_SESSION["user_id"];
$Game4= "Game4";
$gruppen_dayz = $db->prepare("
SELECT g.group_id, g.group_name
FROM groups g
LEFT JOIN users_groups ug
ON g.group_id = ug.group_id
LEFT JOIN group_game gg
ON g.group_id = gg.group_id
LEFT JOIN game ga
ON ga.id = gg.game_id
WHERE ga.game = ? AND ug.user_id = ?
");
$gruppen_dayz->bind_param('ii', $Game4, $user_id);
I don't know exactly how I should build this query :/
Your where clause is being applied after the joins generate the dataset, negating the left join aspect of your joins. To solve this move the criteria to the join itself so the limits are applied before the joins. Otherwise, the NULL values generated in your left joins are then excluded by your where clause.
There may be other elements as well, this is just the first component I saw.
$user_id = $_SESSION["user_id"];
$Game4= "Game4";
$gruppen_dayz = $db->prepare("
SELECT g.group_id, g.group_name
FROM groups g
LEFT JOIN users_groups ug
ON g.group_id = ug.group_id
AND ug.user_id = ?
LEFT JOIN group_game gg
ON g.group_id = gg.group_id
LEFT JOIN game ga
ON ga.id = gg.game_id
AND ga.game = ?
");
$gruppen_dayz->bind_param('ii', $Game4, $user_id);
---UPDATE ----
Upon further investigation I believe your joins are wrong. Groups doesn't have a group_ID field according to your table structure. Walking though the rest now...
SELECT g.group_id, g.group_name
FROM groups g
LEFT JOIN users_groups ug
ON g.id = ug.group_id
LEFT JOIN group_game gg
ON g.id = gg.group_id
LEFT JOIN game ga
ON ga.id = gg.game_id
WHERE ga.game = ? AND ug.user_id = ?
I might rewrite it as...
SELECT G.Id, G.Group_name
FROM USERS_GROUPS UG
INNER JOIN GROUPS G
on UG.Group_ID = G.ID
INNER JOIN GROUP_GAME GG
on GG.Group_ID = G.ID
INNER JOIN Game GA
on GA.ID = GG.Game_ID
WHERE ga.game = ? AND ug.user_id = ?
I see no value or need for left joins based on your criteria.

how to join 3 tables, topic, comment and user

I have 3 tables, tbl_topic, tbl_comment, tbl_user.
I want to select all the topics created by the user and also the topics that he commented on even if he is not the creator. Here is my database:
tbl_topic
----------
topic_id
topic_title
user_id
tbl_comment
----------
comment_id
comment_message
user_id
topic_id
tbl_user
----------
user_id
user_name
Need it so badly. Thanks!
So far i got this
select * from tbl_topic T inner join tbl_comment C on T.topic_id = C.topic_id inner join tbl_user U on T.user_id = U.user_id GROUP BY T.topic_id
My problem is it only returns the topics that has comments on it. I want to include the topics created by the user even if it has 0 comments.
I want the result to be like this:
+-----------+-----------+----------+-------------+----------------+----------+-------
| topic_id | topic_title | user_id | comment_id | comment_message | user_id | topic_id |
+-----------+-----------+----------+-------------+----------------+----------+--------
| 1 | my topic | 1 | 1 | comment me | 1 | 1
| 2 | others | 2 | 2 | comment me | 1 | 2
| 3 | my nocoment| 1 | NULL | NULL | NULL | NULL
+-----------+---------+--------+-------------+----------+----------+---------+--------
----------+-----------+
user_id | user_name |
-----------+-----------
1 | me |
2 | someone |
1 | me
-----------+---------+--
I messed up with my fields in my tables, the user_id beside comment_message should be comment_user_id but i already created my database that way. Can you help make this possible?
The query below uses UNION in the subquery. The first SELECT gets all topics created by user. The second SELECT statement gets all comments of the user and joins it to table tbl_topic so we can get the topic_title.
SELECT topic_ID, topic_title
FROM
(
SELECT a.user_ID, b.topic_ID, b.topic_title
FROM tbl_user a
INNER JOIN tbl_topic b
ON a.user_ID = b.user_ID
UNION
SELECT a.user_ID, c.topic_ID, c.topic_title
FROM tbl_user a
INNER JOIN tbl_comment b
ON a.user_ID = b.user_ID
INNER JOIN tbl_topic c
ON b.topic_ID = c.topic_ID
) x
WHERE x.user_ID = ?
Try the query below. This will show all the fields.
SELECT tt.*, tc.*, tbl_user.*
FROM tbl_topic AS tt INNER JOIN tbl_comment AS tc ON tt.topic_id = tc.topic_id INNER JOIN tbl_user as tc ON tc.user_id = tu.user_id;
WHERE tu.user_id = x
If you have to filter add to the WHERE clause to the query.
Go with a left join. But there is still a Problem left, you will only get ONE table-comment and ONE user. To get more, you can use the GROUP_CONCAT function, like here: http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat
select * from tbl_topic T
LEFT JOIN tbl_comment C on T.topic_id = C.topic_id
LEFT join tbl_user U on T.user_id = U.user_id
WHERE T.user_id = x
GROUP BY T.topic_id
EDIT: the where clause was missing

Trouble with join statement for selecting data across tables with MYSQL

I'm trying to display events that a user has created and events that he has signed up for. I have three tables for this.
//events
| event_id | event_title | event_details | event_timestamp | userid
1 title1 test 1234 1
2 title2 testing2 123 2
//registration_items : event_id references events.event_id
| id | event_id | task_name
1 2 task 1
//registration_signup : id references registration_items.id
| id | userid | timestamp
1 1 1234
Here's the current query I have. Right now it only displays the event the user created. It should display both created events and ones he signed up for
select events.*, registration_items.*, registration_signup.*, users.username from events
INNER JOIN users on users.userid = events.userid
LEFT JOIN registration_items ON registration_items.event_id = events.event_id
LEFT JOIN registration_signup ON registration_signup.id = registration_items.id
WHERE events.userid = '$user_id' OR registration_signup.userid = '$user_id' ORDER BY events.event_timestamp DESC
For userid1 the output should be
Title
title1 (the user created this)
title2 (the user signed up for this)
For userid2 the output should be
Title
title2
select events.*, registration_items.*, registration_signup.*, users.username
from events
INNER JOIN users on users.userid = events.userid
LEFT JOIN registration_items ON registration_items.event_id = events.event_id
LEFT JOIN registration_signup ON registration_signup.id = registration_items.id
WHERE registration_signup.userid = '$user_id'
union
select events.*, registration_items.*, registration_signup.*, users.username
from events
INNER JOIN users on users.userid = events.userid
INNER JOIN registration_items ON registration_items.event_id = events.event_id
INNER JOIN registration_signup ON registration_signup.id = registration_items.id
WHERE events.userid = '$user_id'
ORDER BY events.event_timestamp DESC
I am not sure if it's correct to guess that you have a typo in the sample data. Because your query works the moment you change the user id to 1 for both events, signed up events.. So please take a look at this reference demo and comment if it's not a typo...
SQLFIDDLE DEMO
query: (your query..)
select u.userid,e.event_id as id,
ri.event_id as evt, e.event_title,
ri.task_name,
rs.timestamp,
u.name from events e
INNER JOIN users u on
u.userid = e.userid
LEFT JOIN registration_items ri ON
ri.event_id = e.event_id
LEFT JOIN registration_signup rs ON
rs.id = ri.id
WHERE e.userid = '1' or
rs.userid = '1'
ORDER BY e.event_timestamp DESC
;
Results:
| USERID | ID | EVT | EVENT_TITLE | TASK_NAME | TIMESTAMP | NAME |
------------------------------------------------------------------
| 1 | 1 | 1 | title1 | task 1 | 1234 | john |
| 1 | 2 | 2 | title2 | task 1.2 | 3456 | john |