I have four tables are users(id,name), roles(id,name), members(project_id,user_id,id), and member_roles(member_id, role_id). So how can I select users.name and roles.name from this tables simultaneously(project_id is the condition to select exactly the names what we need)?. I can select users.name and roles.name separately but when I connect two queries, my code was failed. This is the query to get users.name
select users.name from users
inner join members on members.user_id = users.id
where project_id = 1
and here is the query to get roles.name
select roles.name from roles
inner join member_roles on member_roles.role_id = roles.id
join members on members.id = member_roles.member_id
where project_id = 1
You're almost there. Also, to avoid ambiguity, supply an Alias on column Name.
SELECT DISTINCT
u.Name AS member_name,
r.Name AS role_name
FROM users u
INNER JOIN members m
ON u.id = m.user_id
INNER JOIN member_roles mr
ON m.id = mr.member_id
INNER JOIN roles r
ON r.id = mr.role_id
WHERE m.project_id = 1
How do you connect 2 queries? How about something like this:
select u.name as user_name, r.name as role_name from users u join members m on m.user_id = u.id join member_roles mr on mr.member_id = m.id join roles r on r.id = mr.role_id where m.project_id = 1;
Related
i have follwing tables
USERS :
* id
* name
* role id
* phone
STUDENTS
1: userid ( fk users.id)
2: course_id
STAFF
1: staff_id(fk users.id)
2: course-id
COURSES
1: COURSE_ID
1:COURSENAME
I need to find all accounts associated with a number
I need name,userid,roleid,courseid,corsename,staffid, by providing mobile
i have written this query but this return zero results
SELECT users.name, users.id, staff.user_id, students.course_id, users.role_id, courses.course_title FROM users INNER JOIN students ON users.id = students.user_id INNER JOIN staff ON staff.user_id = users.id INNER JOIN courses ON courses.id = students.course_id WHERE users.phone = '9495990028'
LIMIT 0 , 30
Try union operator:
SELECT name, s.userid, roleid, s.course_id, c.coursename, null
FROM USERS u
INNER JOIN STUDENTS s
INNER JOIN COURSES c
ON s.userid = u.id AND c.course_id = s.course_id
WHERE u.phone = ?
UNION
SELECT name, null, roleid, s.course_id, c.coursename, s.staff_id
FROM USERS u
INNER JOIN STAFF s
INNER JOIN COURSES c
ON s.staff_id = u.id AND c.course_id = s.course_id
WHERE u.phone = ?;
For the COURSES table, I check the id with the course_id from students and staff
SELECT name, s.userid, roleid, s.course_id, c.coursename, st.staff_id
FROM USERS u
INNER JOIN STUDENTS s ON s.userid = u.id
INNER JOIN STAFF st ON st.staff_id = u.id
INNER JOIN COURSES c ON c.course_id = s.course_id AND c.course_id = st.course_id
WHERE u.phone = ?
I have Users and Skills table connected through UserSkills table for many-to-many relation. Here is what's in the tables:
Users (id, username)
Skills (id, name)
UserSkills (user_id, skill_id)
I have an array of skills that I am looking for ['C#', 'SQL']. So I am doing join with IN filtering operation to get only those users that I need.
SELECT (username, GROUP_CONCAT(Skills.name)) FROM Users
JOIN UserSkills ON Users.id = UserSkills.user_id
JOIN Skills ON Skills.id = UserSkills.skill_id AND Skills.name IN ('C#', 'SQL')
GROUP BY Users.id
I want to get same users list but with all their skills, not only those that I am looking for. For instance:
In my case I get: username: 'joe' | skills: 'C#', 'SQL'
I want to get: username: 'joe' | skills : 'C#', 'SQL', 'JavaScript', 'NodeJS'
Please help.
The most straight forward way would be to just join a second time:
SELECT u.username, GROUP_CONCAT(DISTINCT userS.name)
FROM Users AS u
INNER JOIN UserSkills AS us ON u.id = us.user_id
INNER JOIN Skills AS filterS ON filterS.id = us.skill_id AND filterS.name IN ('C#', 'SQL')
INNER JOIN Skills AS userS ON userS.id = us.skill_id
GROUP BY u.id
But you will need the DISTINCT in GROUP_CONCAT as the filter skills will basically cross join with the user skills. Also worth noting is this query gets users with any of the skills specified not all. This is a better solution:
SELECT u.username, GROUP_CONCAT(s.name) AS skils
, COUNT(CASE WHEN s.name IN ('C#', 'SQL') THEN 1 ELSE NULL END) AS matchedSkillCount
FROM Users AS u
INNER JOIN UserSkills AS us ON u.id = us.user_id
INNER JOIN Skills AS s ON s.id = us.skill_id
GROUP BY u.id
HAVING matchedSkillCount > 0 -- You can replace 0 with the number of matches you want
;
...but on very large databases, the above might become costly; a couple other alternatives:
SELECT u.username, GROUP_CONCAT(DISTINCT userS.name)
FROM Skills AS filterS
INNER JOIN UserSkills AS ufs ON filterS.id = ufs.skill_id
INNER JOIN Users AS u ON ufs.user_id = u.id
INNER JOIN UserSkills AS us ON u.id = us.user_id
INNER JOIN Skills AS userS ON us.skill_id = userS.id
WHERE filterS.name IN ('C#', 'SQL')
GROUP BY u.id;
SELECT u.username, GROUP_CONCAT(s.name) AS skils
FROM Users AS u
INNER JOIN UserSkills AS us ON u.id = us.user_id
INNER JOIN Skills AS sON s.id = us.skill_id
WHERE u.id IN (
SELECT DISTINCT ufs.user_id
FROM Skills AS filterS
INNER JOIN UserSkills AS ufs ON filterS.id = ufs.skill_id
WHERE filterS.name IN ('C#', 'SQL')
)
GROUP BY u.id
;
Logically, the WHERE is applied after the joins; but most RDBMS (like MySQL) optimize execution by using the WHERE conditions to minimize the rows joined together.
select USERS.name,GROUP_CONCAT(Skills.name) from USERS join USERSKILLS on users.id =
USERSKILLS.user_id join skills on USERSKILLS.SKILL_ID = skills.ID and users.id in (
select distinct users.id from
users join USERSKILLS on users.id = USERSKILLS.user_id join skills on skills.id = userSkills.skill_id and
Skills.name IN ('C#', 'SQL'))
group by USERS.name;
SELECT groups.*
, roles.rol_display_name
, users.usr_fname
FROM groups, groups_roles, roles, users
WHERE groups.id = groups_roles.groups_id and
roles.id = groups_roles.roles_id and
groups.grp_manager_id = users.id
In my query if all the AND conditions are true then only it will show all the records but my requirement is even if manager.id is null it should show all the records with users.usr_fname as null.
Use left join instead of inner join (implicit or otherwise) when you join users table:
SELECT g.*
, r.rol_display_name
, u.usr_fname
FROM groups g
JOIN groups_roles gr on g.id = gr.groups_id
JOIN roles r on r.id = gr.roles_id
LEFT JOIN users u on g.grp_manager_id = u.id
I have a query like that:
SELECT DISTINCT r.name AS role, r.id AS role_id, u.id AS user_id, concat( u.firstname, '', u.lastname ) AS name
FROM users u
INNER JOIN members m ON u.id = m.user_id
INNER JOIN member_roles mr ON m.id = mr.member_id
INNER JOIN roles r ON r.id = mr.role_id
WHERE m.project_id =11
My goal is to get unique u.id(user_id). Unfortunately, the result show two duplicate u.id from this multiple join. If I remove the last one join(INNER JOIN roles r ON r.id = mr.role_id), this query run correctly. But I didn't know why it was wrong if I add this line to my query. The last one join line is necessary to get the role's name, so I can ignore it. Can someone tell me where I did incorrectly in my query?
Use GROUP BY in your query to get rows with unique user_id.
Then the updated query will be look like the following.
SELECT DISTINCT r.name AS role, r.id AS role_id, u.id AS user_id,
concat( u.firstname, '', u.lastname ) AS name
FROM users u
INNER JOIN members m ON u.id = m.user_id
INNER JOIN member_roles mr ON m.id = mr.member_id
INNER JOIN roles r ON r.id = mr.role_id
WHERE m.project_id =11 GROUP BY user_id
You are missing the fact that users can have multiple roles on a project. Fortunately, MySQL has group_concat() which can bring the multiple values together:
SELECT u.id AS user_id, concat( u.firstname, '', u.lastname ) AS name,
GROUP_CONCAT(r.name) as roles,
GROUP_CONCAT(r.id) as role_ids
FROM users u INNER JOIN
members m
ON u.id = m.user_id INNER JOIN
member_roles mr ON m.id = mr.member_id INNER JOIN
roles r
ON r.id = mr.role_id
WHERE m.project_id = 11
GROUP BY u.id;
I have two tables, users and contestants. I'm trying to select the max contestant ID that has a profile picture(which is on the user table)
Heres my terrible SQL:
SELECT u.thumbnail, u.id FROM users AS u
INNER JOIN
(
SELECT c.id, c.user_id FROM contestants AS c
WHERE u.id = c.users_id
AND c.id = (select max(c.id))
) WHERE u.thumbnail IS NOT NULL
The error currently is: #1248 - Every derived table must have its own alias.
This confuses me since Users has an alias of u, and contestants has an alias of c..
What am I doing wrong here? I'm guessing a lot so some help would be really appreciated!
Whenever you are performing a join operation, you are actually joining two table. The subquery you wrote here, for instance, is working as a separate table. Hence, you have to use an alias to this table. That's the reason behind your error message.
Your query:
SELECT u.thumbnail, u.id FROM users AS u
INNER JOIN
(
SELECT c.id, c.user_id FROM contestants AS c
WHERE u.id = c.users_id
AND c.id = (select max(c.id))
) WHERE u.thumbnail IS NOT NULL
It should contain an alias for the subquery:
SELECT c.id, c.user_id FROM contestants AS c
WHERE u.id = c.users_id
AND c.id = (select max(c.id))
Let's say, it's T.
So, your query now becomes:
SELECT u.thumbnail, u.id FROM users AS u
INNER JOIN
(
SELECT c.id, c.user_id FROM contestants AS c
WHERE u.id = c.users_id
AND c.id = (select max(c.id))
) AS T
WHERE u.thumbnail IS NOT NULL
But what you are trying to achieve, can actually be done in a neater way:
SELECT u.thumbnail, u.id, max(c.id),
FROM users as u
LEFT JOIN contestants as c
on u.id = c.user_id
WHERE u.thumbnail IS NOT NULL
Why make all the fuss when you have a better and neater approach at your disposal?
try this:
SELECT u.thumbnail, u.id
FROM users AS u
INNER JOIN
(
SELECT c.id, c.user_id FROM contestants AS c
WHERE u.id = c.users_id
AND c.id = (select max(c.id))
)A
WHERE u.thumbnail IS NOT NULL
i think this should be simple,
SELECT u.thumbnail, u.id
FROM users u
INNER JOIN contestants c
ON u.id = c.users_id
WHERE u.thumbnail IS NOT NULL
ORDER BY c.id DESC
LIMIT 1
This is very simple.
SELECT user.thumbnail, user.id
FROM users user
INNER JOIN contestants cont ON cont.id = cont.users_id
WHERE cont.thumbnail IS NOT NULL
ORDER BY user.id DESC