What I want is the Participants (people, with role as participant) of one event, combined with people of the same companies as that of participants, but whose role is manager.
A Person's role is stores in person_role_membership, but a person's company is stored in People. I have crafted the following query, which I think does the job pretty well. Please ignore the extra joins and information. I am fetching all the participants, then UNION-ing with all the managers, for which I am once again fetching all the participants. Now the trouble is this whole query, for a small subset is taking 9 seconds. Is there a way to make it faster?
select distinct *
from
(
SELECT
p.id as p_id, p.first_name as p_first_name, p.last_name as p_last_name,p_r.name as p_role,
p.job_title as p_job_title,
p_d.email as p_email, p_d.phone_1 as p_phone, p_d.phone_ext_1 as p_ext,
c.name as p_company, p_c.name as p_parent_company
FROM person_role_memberships as prm
left join people as p on prm.person_id = p.id and prm.person_role_id between 32 and 35
left join person_roles as p_r on p_r.id = prm.person_role_id
left join person_details as p_d on p.id = p_d.person_id and p_d.type = 'BusinessDetail'
left join companies as c on c.id = p.company_id
left join companies as p_c on p_c.id = p.parent_company_id
where
p.id is not null
) as parts
union (
select p.id, p.first_name,p.last_name,prm.person_role_id, p.job_title, 'cp email', 'phone','ext',c.name, d.name
from people as p -- All those people
left join person_role_memberships as prm on prm.person_id = p.id -- whose roles are like this
left join companies as c on p.company_id = c.id
left join companies as d on c.parent_id = d.id
-- and whose companies are like those people whose roles are like this
where company_id = any
(
select company_id from people as p
left join person_role_memberships as prm on prm.person_id = p.id
where prm.person_role_id between 32 and 35-- and other conditions;
)
and (person_role_id = 14 or person_role_id = 15))
My guess would be that the 'any' part of your query is slowing things down. By the looks of it I think you don't even need it because you could filter on person_role_memberships directly:
select p.id, p.first_name,p.last_name,prm.person_role_id, p.job_title, 'cp email', 'phone','ext',c.name, d.name
from people as p -- All those people
left join person_role_memberships as prm on prm.person_id = p.id -- whose roles are like this
left join companies as c on p.company_id = c.id
left join companies as d on c.parent_id = d.id
-- and whose companies are like those people whose roles are like this
where prm.person_role_id between 32 and 35 -- and other conditions;
and (person_role_id = 14 or person_role_id = 15))
The 'any'-statement is causing the database to look through the entire PEOPLE table for every record.
Related
I have a wordpress site that is used to store student grades on various lessons (from the quizzes on the site). I am trying to create a query that will pull out all of the lessons for all students in a certain group (using buddypress groups) and the students grades in each lesson.
I have created this query:
SELECT u.display_name, p.post_title, cm.meta_value
FROM wp_users u
JOIN wp_bp_groups_members gm
ON u.ID = gm.user_id
JOIN wp_comments c
ON u.ID = c.user_id
JOIN wp_commentmeta cm
ON c.comment_ID = cm.comment_id
JOIN (SELECT * FROM wp_posts WHERE post_type LIKE 'lesson') p
ON c.comment_post_id = p.ID
WHERE gm.group_id = 4 AND cm.meta_key LIKE 'grade'
This currently returns all the grades for all students in a group in the lessons they have attempted the test. However it does not return any lessons they have not attempted the test in, which I need still.
Just to be clear: lessons are posts, grades are meta_values in a record with a meta_key of 'grades'. These are stored as comments, and comment_meta.
I hope this is all clear and you can help. Thanks.
After Ollie Jones help I made this:
SELECT u.display_name, p.post_title, IFNULL(cm.meta_value,'--nothing--') grade
FROM wp_users u
JOIN wp_comments c
LEFT JOIN wp_commentmeta cm
ON c.comment_ID = cm.comment_id AND cm.meta_key = 'grade'
JOIN wp_bp_groups_members gm
ON u.ID = gm.user_id
JOIN wp_posts p
ON c.comment_post_id = p.ID
WHERE gm.group_id = 4 AND p.post_type LIKE 'lesson'
Which almost works but returns all student grades, not just the ones in the group (though it only gives the one name of the student in the group).
This is the familiar key/value store problem, that comes up with commentmeta, postsmeta, and usermeta. When you JOIN two tables and the left one might not have a corresponding row, you need to use LEFT JOIN. When the left one is a key/value table, you need to adjust the ON condition accordingly. Finally, when you LEFT JOIN two tables and there's no matching row in it it, you get back NULLs for those columns, so you must allow for that.
So this kind of SQL pattern will do the trick for you
SELECT whatever, IFNULL(cm.meta_value,'--nothing--') grade
FROM whatever
LEFT JOIN wp_comments c ON whatever.id = c.user_id
LEFT JOIN wp_commentmeta cm ON c.comment_id = cm.comment_id
AND cm.meta_key = 'grade'
JOIN whatever
Is there a user_id in your comments table? I dont see where you joined which user posted which comment. So when you join the group_members to the users table, you are specifying which users to show, but since you are not joining on user id when you join to your comments table, it will show all the comments for all the users. Im not sure if this will work for your table, but try:
SELECT u.display_name, p.post_title, IFNULL(cm.meta_value,'--nothing--') grade
FROM wp_users u
LEFT JOIN wp_comments c
JOIN wp_commentmeta cm
ON c.comment_ID = cm.comment_id AND cm.meta_key = 'grade'
JOIN wp_bp_groups_members gm
ON c.user_ID = gm.user_id
ON u.user_id = c.user_id
JOIN wp_posts p
ON c.comment_post_id = p.ID
WHERE gm.group_id = 4 AND p.post_type LIKE 'lesson'
Hope this helps!
I have a database with the tables:
Student(SID,Name,Surname,Age)
Registration(StudentID,CourseID)
Course(CID,Name,Cost)
I would like to extract only the name of the courses with students younger than 20. Will the query below do just that?
SELECT C.NAME
FROM Course C
INNER JOIN Registration
INNER JOIN Student S
WHERE CID = CourseID
AND SID = StudentID
AND Age < 20
GROUP BY C.NAME
I would also like to extract the number of students in each course having students younger than 20. Is it correct to do it as below?
SELECT count(S.NAME)
,C.NAME
FROM Student S
INNER JOIN Course C
INNER JOIN Registration
WHERE Age < 20
AND CID = CourseID
AND SID = StudentID
GROUP BY C.NAME
You are missing the ON part for the join otherwise it would just be a CROSS JOIN.
Your first query should look like this if you want just a distinct list of student names:
SELECT DISTINCT C.NAME
FROM Course C
INNER JOIN Registration R ON C.CID = R.CourseID
INNER JOIN Student S ON R.StudentID = S.SID
WHERE Age < 20
Your second query shouldn't really have the C.Name in the select if you want to get just a count unless you want a count of how many students have that name.
SELECT count(*)
FROM Student S
INNER JOIN Registration R ON s.SID = R.StudentID
INNER JOIN Course C ON c.CID = R.CourseID
WHERE Age < 20
GROUP BY C.NAME
First join these tables, then group by Course's PK(CID), Add the HAVING condition to filter the course which has students younger than 20.
Then use Course table to join the result to get the course name and count of students in the course.
SELECT
T1.Name,
T2.StudentCount
FROM
Course T1
INNER JOIN (
SELECT
c.CID,
COUNT(s.SID) AS StudentCount
FROM
Course c
LEFT JOIN Registration r ON c.CID = r.CourseID
LEFT JOIN Student s ON s.SID = r.StudentID
GROUP BY c.CID
HAVING COUNT(IF(s.Age < 20, 1, NULL)) > 0
) T2 ON T1.CID = T2.CID
More correctly, you should move the conditions of the join, to the join statements themselves by including them in the on clause instead of the where. While the results may not change in this instance, if you were to start including outer joins you would encounter difficulties.
SELECT count(S.NAME)
,C.NAME
FROM Student S
INNER JOIN Registration R
ON s.SID = R.StudentID
INNER JOIN Course C
ON c.CID = R.CourseID
WHERE Age < 20
GROUP BY C.NAME
There's a fiddle here showing it in action: http://sqlfiddle.com/#!9/c3b8f/1
Your first query will also produce the results you want, but again, you should move the join predicates to the join itself. Also, you don't need to perform the grouping just to get distinct values, mysql has an expression for that called distinct. So rewritten, the first query would look like:
SELECT DISTINCT C.NAME
FROM Student S
INNER JOIN Registration R
ON s.SID = R.StudentID
INNER JOIN Course C
ON c.CID = R.CourseID
WHERE Age < 20.
Again, the results are the same as what you have already but it is easier to 'read' and will put you in good stead when you move on to other queries. As it stands you have mixed implicit and explicit join syntax.
This fiddle demonstrates both queries: http://sqlfiddle.com/#!9/c3b8f/4
edit
I may have misinterpreted your original question - if you want the total number of students enrolled in a course with at least one student under 19, you can use a query like this:
select name, count(*)
from course c
inner join registration r
on c.cid = r.courseid
where exists (
select 1
from course cc
inner join registration r
on cc.cid = r.courseid
inner join student s
on s.sid = r.studentid
where cc.cid = c.cid
group by cc.cid
having min(s.age) < 20
)
group by name;
Again with the updated fiddle here: http://sqlfiddle.com/#!9/c3b8f/17
I have three tables in Mysql that are link together:
Profile (ID, Name, Stuff..)
Contact(ID, ProfileID,desc,Ord)
Address(ID,ProfileID, desc, Ord)
Now I need to select all profile from the profile table, with the “desc” field from Contact and Address where Ord = 1. (this is for a search function where in a table I’ll display the name, main contact info and main Address of a client.
I can currently do this with three separate SQL request:
SELECT Name, ID FROM Profile WHERE name=”bla”
Then in a foreach loop, I’ll run the other two requests:
SELECT ProfileID, desc FROM Contact WHERE ProfileID=MyProfileID AND Ord=1
SELECT ProfileID, desc FROM Address WHERE ProfileID=MyProfileID AND Ord=1
I know you can do multiple SELECT in one query, is there a way I could group all three SELECT into one query?
You should be able to JOIN the tables on the profile.id and the profileid in the other tables.
If you are sure the profileid exists in all three tables, then you can use an INNER JOIN. The INNER JOIN returns matching rows in all of the tables:
select p.id,
p.name,
c.desc ContactDesc,
a.desc AddressDesc
from profile p
inner join contact c
on p.id = c.profileid
inner join address a
on p.id = a.profileid
where p.name = 'bla'
and c.ord = 1
and a.ord = 1
If you are not sure that you will have matching rows, then you can use a LEFT JOIN:
select p.id,
p.name,
c.desc ContactDesc,
a.desc AddressDesc
from profile p
left join contact c
on p.id = c.profileid
and c.ord = 1
left join address a
on p.id = a.profileid
and a.ord = 1
where p.name = 'bla'
If you need help learning JOIN syntax, here is a great visual explanation of joins
This query below only selects column when an ID from Profile table has atleast one match on tables: Contact and Address. If one or both of them are nullable, use LEFT JOIN instead of INNER JOIN because LEFT JOIN displays all records from the Left-hand side table regardless if it has a match on other tables or not.
SELECT a.*,
b.desc as BDESC,
c.desc as CDESC
FROM Profile a
INNER JOIN Contact b
ON a.ID = b.ProfileID
INNER JOIN Address c
ON a.ID = c.ProfileID
WHERE b.ORD = 1 AND
c.ORD = 1 AND
a.Name = 'nameHERE'
The LEFT JOIN version:
SELECT a.*,
b.desc as BDESC,
c.desc as CDESC
FROM Profile a
INNER JOIN Contact b
ON a.ID = b.ProfileID AND b.ORD = 1
INNER JOIN Address c
ON a.ID = c.ProfileID AND c.ORD = 1
WHERE a.Name = 'nameHERE'
To further gain more knowledge about joins, kindly visit the link below:
Visual Representation of SQL Joins
i have created working demo as your requirement :
The query bellow will retrieve all matching records from the database.its retrieving profile id,name stufff and description of contact tables
select p.id,p.name,p.stauff,c.descr,a.descr from profile as p
inner join contact as c on c.profileid=p.id
inner join address as a on a.profileid=p.id
where p.name="bla" and c.ord=1 and a.ord=1
I am working on expanding user profiles for my project, adding more info. I was just adding countries, when I hit a problem. This is my query for selecting all profile data needed:
SELECT c.*, d.username, d.email, e.country_name
FROM user_profiles c, users d, country e
WHERE c.user_id = ".$id." AND d.id = ".$id."
AND e.country_name = (SELECT country_name FROM country WHERE id = c.country_id)
c.* should select all columns from user_profiles.
The $id is an id of user selecting wich profile should be returned. The problem is, keeping registration as simple as possible, I dont have a country selector there. So when this query comes in action, column country_id from user_profiles is empty, that means when I want to return the country_name, the query result is empty, so no profile data is returned.
I have tried to rewrite this with CASE or LEFT JOIN, but I think I am missing something. I want to find if country_id is not null, when it is not, select also country_name with this country_id. Any ideas?
Thank you kindly for responds.
You can use a LEFT JOIN, but it would be so much easier to do that if you started off by using the cleaner and more modern JOIN syntax:
SELECT c.*, d.username, d.email, e.country_name
FROM user_profiles c
JOIN users d ON d.id = c.id
JOIN country e ON e.country_id = c.country_id
WHERE c.user_id = 42
Now to solve your problem you can just add LEFT:
LEFT JOIN country e ON e.country_id = c.country_id
Full query:
SELECT c.*, d.username, d.email, e.country_name
FROM user_profiles c
JOIN users d ON d.id = c.id
LEFT JOIN country e ON e.country_id = c.country_id
WHERE c.user_id = 42
Related
Why isn't SQL ANSI-92 standard better adopted over ANSI-89?
Before I even start thinking about your current problem, can I just point out that your current query is a mess. Really bad. It might work, it might even work efficiently - but it's still a mess:
SELECT c.*, d.username, d.email, e.country_name
FROM user_profiles c, users d, country e
WHERE d.id = ".$id."
AND d.id = c.user_id
AND e.id = c.country_id;
I have tried to rewrite this with CASE or LEFT JOIN
But you're not going to show us your code?
One solution would be to use a sub select against each row in user_profiles/users:
SELECT c.*, d.username, d.email,
(SELECT e.country_name
FROM country e
WHERE AND e.id = c.country_id LIMIT 0,1) AS country_name
FROM user_profiles c, users d
WHERE d.id = ".$id."
AND d.id = c.user_id;
Alternatively, use a LEFT JOIN:
SELECT c.*, d.username, d.email, e.country_name
FROM user_profiles c
INNER JOIN users d
ON d.id = c.user_id
LEFT JOIN country e
ON e.id = c.country_id
WHERE d.id = ".$id.";
Just wondering what's a better way to write this query. Cheers.
SELECT r.user_id AS ID, m.prenom, m.nom
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id
LEFT JOIN `0_user` AS m ON r.user_id = m.id
WHERE r.section_id = $section_id
AND l.rank = '$rank_name' AND depart_id IN
(SELECT depart_id FROM 0_depart WHERE user_id = $user_id AND section_id = $section_id)
GROUP BY r.user_id
Here are the table structures:
0_rank: id | section_id | rank_name |
other_stuffs
0_user: id | prenom | nom | other_stuffs
0_right: id | section_id | user_id |
rank_id | other_stuffs
0_depart: id | section_id | user_id | depart_id
| other_stuffs
The idea is to use the same in a function like:
public function usergroup($section_id,$rank_name,$user_id) {
// mysql query goes here to get a list of appropriate users
}
Update: I think I have not been able to express myself clearly earlier. Here is the most recent query that seems to be working.
SELECT m.id, m.prenom, m.nom,
CAST( GROUP_CONCAT( DISTINCT d.depart ) AS char ) AS deps,
CAST( GROUP_CONCAT( DISTINCT x.depart ) AS char ) AS depx
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id
LEFT JOIN `0_member` AS m ON r.user_id = m.id
LEFT JOIN `0_depart` AS d ON m.id = d.user_id
LEFT JOIN `0_depart` AS x ON x.user_id = $user_id
WHERE r.section = $section_id
AND l.rank = '$rank_name'
GROUP BY r.user_id ORDER BY prenom, nom
Now I want to get only those result, where all entries of deps are present in entries in depx.
In other term, every user is associated with some departs. $user_id is also an user is associated with some departs.
I want to get those users whose departs are common to the departs of $user_id.
Cheers.
Update
I'm not sure without being able to see the data but I believe this query will give you the results you want the fastest.
SELECT m.id, m.prenom, m.nom,
CAST( GROUP_CONCAT( DISTINCT d.depart ) AS char ) AS deps,
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id and r.user_id = $user_id
LEFT JOIN `0_member` AS m ON r.user_id = m.id
LEFT JOIN `0_depart` AS d ON m.id = d.user_id
WHERE r.section = $section_id
AND l.rank = '$rank_name'
GROUP BY r.user_id ORDER BY prenom, nom
Let me know if this works.
Try this:
(By converting the functionality of the IN (SELECT...) to an inner join, you get exactly the same results but it might be the optimizer will make better choices.)
SELECT r.user_id AS ID, m.prenom, m.nom
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id and r.section_id = 2
LEFT JOIN `0_user` AS m ON r.user_id = m.id
INNER JOIN `0_depart` AS x ON l.section_id = x.section_id and x.user_id = $user_id AND x.section_id = $section_id
WHERE l.rank = 'mod'
GROUP BY r.user_id
I also moved the constraints on 0_right to the join statement because I think that is clearer -- presumably this change won't matter to the optimizer.
I know nothing about your DB structure but your subselect looks like it can be replaced with a simple INNER JOIN against whatever table has the depart column. MySQL is well known for its poor subquery optimization.
Without knowing the structures or indexes, I would first add "STRAIGHT_JOIN" if the critical criteria is in-fact from the 0-rank table. Then, ensure 0_rank has an index on "rank". Next, ensure the 0_right has an index on rank_id at a minimum, but rank_id, section to take advantage of BOTH your criteria. Index on 0_member on id.
Additionally, do you mean left-join (ie: record only required in the 0_rank or 0_member) on the respective 0_right and 0_member tables instead of a normal join (where BOTH tables must match on their IDs).
Finally, ensure index on the depart table on user_id.
SELECT STRAIGHT_JOIN
r.user_id AS ID,
m.prenom,
m.nom
FROM
0_rank AS l
LEFT JOIN `0_right` AS r
ON l.id = r.rank_id
AND r.section = 2
LEFT JOIN `0_member` AS m
ON r.user_id = m.id
WHERE
l.rank = 'mod'
AND depart IN (SELECT depart
FROM 0_depart
WHERE user_id = 2
AND user_sec = 2)
GROUP BY
r.user_id
---- revised post from feedback.
From the parameters you are listing, you are always including the User ID... If so, I would completely restructure it to get whatever info is for that user. Each user should apparently can be associated to multiple departments and may or may NOT match the given rank / department / section you are looking for... I would START the query with the ONE USER because THAT will guarantee a single entry, THEN tune-down to the other elements...
select STRAIGHT_JOIN
u.id,
u.prenom,
u.nom,
u.other_stuffs,
rank.rank_name
from
0_user u
left join 0_right r
on u.id = r.user_id
AND r.section_id = $section_id
join 0_rank rank
on r.rank_id = rank.id
AND rank.rank_name = '$rank_name'
left join 0_dept dept
on u.id = dept.user_id
where
u.id = $user_id
Additionally, I have concern about your table relationships and don't see a legit join to the department table...
0_user
0_right by User_ID
0_rank by right.rank_id
0_dept has section which could join to rank or right, but nothing to user_id directly
Run explain on the query - it will help you find where the caveats are:
EXPLAIN SELECT r.user_id AS ID, m.prenom, m.nom
FROM 0_rank AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id
LEFT JOIN `0_member` AS m ON r.user_id = m.id
WHERE r.section = 2
AND l.rank = 'mod' AND depart IN
(SELECT depart FROM 0_depart WHERE user_id = 2 AND user_sec = 2)
GROUP BY r.user_id\G