I have a renting schema in my database.
It has 3 tables, user, rentingTrack and lock.
user has as unique element RFIDCode.
in rentingTrack I may have the user(he or she rented at least once) or not (he/she never rented). If the user rented I need the returnLock for the last rent, as rentingID is autoincremented, it is max(rentingID).
With lock table I got the parkingID, the data I need.
The problem is how to get the parkingID, I have half query:
SELECT u.userID, l.parkingID
FROM locks l, user u
LEFT JOIN (SELECT r1.* FROM rentingTrack r1 INNER JOIN
(SELECT userID, MAX(rentingID) maxRentingID FROM rentingTrack GROUP BY userID) r2
on r1.rentingID = r2.maxRentingID) r on u.userID = r.userID
WHERE u.userCodeRFID= 3166681355
What i need is, if userID isn't in the rentingTrack table I got:
userID | parkingID
----------+-----------
34 | NULL
And if userID is in the rentingTrack
userID | parkingID
----------+-----------
34 | 5
how can I complete the query to get parkingID?
Try This. (Need some sample data for duplicates)
select distinct u.userID,l.parkingID
from users
left join rentingTrack r on u.userID=r.userID
left join locks l on r.returnLock=l.lockid
SELECT u.userID, l.parkingID
FROM user u
LEFT JOIN (SELECT r1.userID, r1.returnLock
FROM rentingTrack r1
INNER JOIN
(SELECT userID, MAX(rentingID) maxRentingID
FROM rentingTrack
GROUP BY userID) r2
ON r1.rentingID = r2.maxRentingID) r on u.userID = r.userID
LEFT JOIN locks l ON r.returnLock = l.lockID
WHERE u.userCodeRFID= 3166681355
Related
I have two tables one is users and second is user_education.One users can have more than one education listing so i want to get the latest user education listing
users
===============
1-id
2-email
member_experience
==============
1-id
2-user_id
3-designation
user id 1 has 4 enteries in user_education so i want to get the last record enter designation of the user
original full query is like this
SELECT u.id,u.name,u.gender,u.email,file_managed.file_name,file_managed.file_path
from users as u
INNER JOIN member_experience on (SELECT uid FROM member_experience where member_experience.uid=u.id ORDER BY id DESC LIMIT 1)=u.id
LEFT JOIN file_managed on file_managed.id= u.fid
where u.user_type ='individual' AND u.gender='male'
"INNER JOIN member_experience on (SELECT uid FROM member_experience where member_experience.uid=u.id ORDER BY id DESC LIMIT 1)=u.id "
this portion has problem as users has many record in member_experience table but i want to get only one which is latest.
thanks
Devolve the acquisition of the last record to the where statement.
drop table if exists member_experience;
create table member_experience(id int auto_increment primary key, userid int);
insert into member_experience (userid) values
(1),(2),(1);
select * from member_experience
SELECT u.id,m.id
from users as u
join member_experience m on m.userid = u.id
where m.id = (SELECT max(m.id) FROM member_experience m where m.userid = u.id)
order by u.id
Or if you want to include those with no experience
SELECT u.id,m.id
from users as u
left join member_experience m on m.userid = u.id
where (m.id = (SELECT max(m.id) FROM member_experience m where m.userid = u.id)
or m.id is null)
and u.id < 4
order by u.id
I've this table structure:
-request
request_id
user_id
-user
user_id
company_id
-company
company_id
I want to select all those records from requests table where user_id=? and no such records where the company id of to users is same.
This is usually achieved using LEFT JOIN:
SELECT r.*
FROM request r
JOIN user u ON r.user_id = u.user_id
LEFT JOIN u1 ON u1.user_id != u.user_id AND u1.company_id = u.company_id
LEFT JOIN request r1 ON r1.user_id = u1.user_id
WHERE r1.user_id IS NULL
By "where" we say that we don't want "users with same company, who has at least 1 request"
I have 3 tables: tickets, tickets_users and users. My problem is that in the users table I have 2 types of users: requesters and solvers: type 1 and 2.
I want to select the ticket, requester (if any, can be multiple) and solver (if any, can be multiple).
I'm thinking something in the lines of:
SELECT
t.id, t.description,
(u.id where u.type = 1) AS requester,
(u.id where u.type = 2) AS solver
FROM
tickets t
INNER JOIN
tickets_users tu ON t.id = tu.ticket_id
INNER JOIN
users u ON tu.user_id = u.id
Obviously this does not work.
The tables look like this:
Tickets:
ID Description
1 Description 1
2 Description 2
Tickets_users
ID Ticket_ID User_id Type
1 3 4 1
2 5 8 2
Users
ID Name
1 John
2 Mary
Thanks,
In the meantime I think I found a solution using a sub-query in the join clause, but to me it looks rudimentary:
SELECT
t.id, t.name AS ticket_name, type1.users_id AS requester,
type2.users_id AS solver
FROM
tickets t
INNER JOIN
(SELECT users_id, tickets_id
FROM tickets_users
WHERE TYPE = 1) type1 ON t.id = type1.tickets_id
INNER JOIN
(SELECT users_id, tickets_id
FROM tickets_users
WHERE TYPE = 2) type2 ON t.id = type2.tickets_id
Should be something like this.
SELECT
t.id, t.description, u.id, userType
CASE WHEN u.type = 1 THEN 'requester' ELSE 'solver' END
FROM
tickets t
INNER JOIN tickets_users tu ON t.id = tu.ticket_id
INNER JOIN users u ON tu.user_id = u.id
Please provide sqlfiddle in case above example does not work.
With Joins,
SELECT
t.id, t.description, requesters.id, solvers.id
FROM
tickets t
INNER JOIN tickets_users tu ON t.id = tu.ticket_id
LEFT JOIN users requesters ON (tu.user_id = requesters.id AND requesters.type=1)
LEFT JOIN users solvers ON (tu.user_id = solvers.id AND solvers.type=2)
As you can tell, users table is joined twice (as requesters and as solvers with additional conditions). The reason LEFT JOIN is used is because if there's a record with no requesters or no solvers, INNER JOIN would completely ignore the whole record until it has a requester and a solver.
It must be pretty easy, but i can't think of any solution nor can I find an answer somewhere...
I got the table 'users'
and one table 'blogs' (user_id, blogpost)
and one table 'messages' (user_id, message)
I'd like to have the following result:
User | count(blogs) | count(messages)
Jim | 0 | 3
Tom | 2 | 3
Tim | 0 | 1
Foo | 2 | 0
So what I did is:
SELECT u.id, count(b.id), count(m.id) FROM `users` u
LEFT JOIN blogs b ON b.user_id = u.id
LEFT JOIN messages m ON m.user_id = u.id
GROUP BY u.id
It obviously doesn't work, because the second left join relates to blogs not users. Any suggestions?
First, if you only want the count value, you could do subselects:
select u.id, u.name,
(select count(b.id) from blogs where userid = u.id) as 'blogs',
(select count(m.id) from messages where userid = u.id) as 'messages'
from 'users'
Note that this is just a plain sql example, I have no mysql db here to test it right now.
On the other hand, you could do a join, but you should use an outer join to include users without blogs but with messages. That would imply that you get several users multiple times, so a group by would be helpful.
If you use an aggregate function in a select, SQL will collapse all your rows into a single row.
In order to get more than 1 row out you must use a group by clause.
Then SQL will generate totals per user.
Fastest option
SELECT
u.id
, (SELECT(COUNT(*) FROM blogs b WHERE b.user_id = u.id) as blogcount
, (SELECT(COUNT(*) FROM messages m WHERE m.user_id = u.id) as messagecount
FROM users u
Why you code does not work
SELECT u.id, count(b.id), count(m.id)
FROM users u
LEFT JOIN blogs b ON b.user_id = u.id <<-- 3 matches multiplies # of rows *3
LEFT JOIN messages m ON m.user_id = u.id <<-- 5 matches multiplies # of rows *5
GROUP BY u.id
The count will be off, because you are counting duplicate items.
Simple fix, but will be slower than option 1
If you only count distinct id's, you will get the correct counts:
SELECT u.id, count(DISTNICT b.id), count(DISTINCT m.id)
FROM users u
LEFT JOIN blogs b ON b.user_id = u.id
LEFT JOIN messages m ON m.user_id = u.id
GROUP BY u.id
I have 3 tables in my mysql DB to query.
Users_rates (fields: id,userid,raterid,rate,eventid) containing all of the rates(rate) that have been assigned to users(userid), participating to specific events(eventid), by other users(raterid)
Events_participants (fields:id,userid,eventid) containing all of the users(userid) participating to each event(eventid)
Users (fields:id,name,lastname)containing all the user relative data
I need to query those three tables to retrieve an event-specific rank for the users' rates.
Ex. John,Erik and Mark participated to 'eventid=31'.
John received 1 rate from Mark, and 2 from Erik.
Mark received 1 rate from Erik.
Nobody has rated Erik though.
I need to retrieve for each user name,lastname and the sum of the rates received for eventid=31
I tried with this:
SELECT events_participants.userid,users.name,users.lastname,
(SELECT SUM(rate)FROM users_rates WHERE users_rates.eventid=31 AND users_rates.userid=events_participants.userid)AS rate
FROM(( events_participants INNER JOIN users ON events_participants.userid=users.id)
LEFT OUTER JOIN users_rates ON events_participants.userid=users_rates.userid )
WHERE events_participants.eventid=31
But I receive:
userid | name | lastname | rate
1 | luca | silvestro | 1
3 | claudio | buricchi | 6
3 | claudio | buricchi | 6
What's the right query?
Thanks
Luca
Try this:
SELECT users.userid, users.name, users.lastname, temp.sum as rate
FROM users LEFT JOIN (
SELECT userid, SUM(rate) as sum FROM users_rates WHERE eventid = 31 GROUP BY userid
) as temp USING (userid)
It might give an error, this might work instead:
SELECT users.userid, users.name, users.lastname, temp.sum as rate
FROM users, (
SELECT userid, SUM(rate) as sum FROM users_rates WHERE eventid = 31 GROUP BY userid
) as temp WHERE users.userid = temp.userid
I don't know if I got the problem right, but maybe something like:
SELECT u.id, u.name, u.lastname, SUM(ur.rate) AS rate
FROM users AS u
INNER JOIN users_rates AS ur ON ur.userid = u.id
WHERE ur.eventid = 31
GROUP BY u.id
edit: If you want to receive a list with all users regardless of whether they have any rates at all, you could also join the users_participants table and replace the INNER JOIN of users_rates by a LEFT JOIN. The WHERE clause has to reference events_participants then (not users_rates anymore as it could be NULL):
SELECT u.id, u.name, u.lastname, SUM(ur.rate) AS rate
FROM users AS u
INNER JOIN events_participants AS ep ON ep.userid = u.id
LEFT JOIN users_rates AS ur ON ur.userid = u.id AND ur.eventid = ep.eventid
WHERE ep.eventid = 31
GROUP BY u.id