I have two columns one for users(including student and teacher) and other for teacher_subscription. I want to select users(teacher) which are not followed by current user(for e.g user1).
i tried this..
select users.uid,acctype,uname from users where uid!=1 && acctype='Teacher'&& users.uid not in (select tid from teacher_subscription where uid!=1&&tid!=users.uid)
but not getting desire results
I have two columns one for users(including student and teacher) and other for teacher_subscription. I want to select users(teacher) which are not followed by current user(for e.g user1).
i tried this..
select users.uid,acctype,uname from users where uid!=1 && acctype='Teacher'&& users.uid not in (select tid from teacher_subscription where uid!=1&&tid!=users.uid)
but not getting desire results
try this?
select users.uid,acctype,uname from users where acctype='Teacher'&& users.uid not in (select tid from teacher_subscription where uid=1)
Related
I want to get Users' info with their last dates of login.
select * from Users as UU
inner join
(select user_id, max(d_login) from Logins group by user_id) as LL
on UU.user_id = LL.user_id
Join doesn't work in VFP. We can't join table to query here?
VFP need to use ALLTRIM() in join, otherwise comparing 2 values could result undesirable data. your code should be like this
select * from Users as UU
inner join
(select user_id, max(d_login) from Logins group by
user_id) as LL
on ALLT(UU.user_id) == ALLT(LL.user_id)
Assuming you have normalised User_ID as primary key in both tables i.e. Users and Logins and have same Field Type and Field Length. I created the tables users and Logins and tested this query with a sample data and it worked smoothly and gave exact results.
select
Users.User_id,
Users.Cell1,
Users.Name,
max(d_login)
from Logins, users
WHERE users.user_id = logins.user_id
GROUP BY
Users.user_id, Users.Cell1, Users.Name, Logins
I have two tables, neither with a primary id. The same combination of fields uniquely identifies the records in each and makes the records between the two tables relate-able (I think).
I need a query to combine all the records from one table and only the records from the second not already included from the first table. How do I do this using 'not equal to' joins on multiple fields? My results so far only give me the records of the first table, or no records at all.
Try the following:
SELECT ECDSlides.[Supplier Code], ECDSlides.[Supplier Name], ECDSlides.Commodity
FROM ECDSlides LEFT JOIN (ECDSlides.Commodity = [Mit Task Details2].Commodity) AND (ECDSlides.[Supplier Code] = [Mit Task Details2].[Supplier Code])
WHERE [Mit Task Details2].Commodity Is Null;
This might be what you are looking for
SELECT fieldA,fieldB FROM tableA
UNION
SELECT fieldA,fieldB FROM tableB
Union should remove automatically. 'Union All' would not.
If, for some reason, you get perfect duplicates and they are not removed, you could try this :
SELECT DISTINCT * FROM (
SELECT fieldA,fieldB FROM tableA
UNION
SELECT fieldA,fieldB FROM tableB
) AS subquery
We have 2 tables: users and statuses
The status table has a user_id, status and occured_on. The status is either 'removed' or 'added' and occured_on is the date the user was removed or added.
I need the current added users. That is, all the (distinct) users whose newest status record is 'added'.
I'm using Rails, and have tried:
User
.joins(:statuses)
.where('statuses.status = ?', 'added')
.order('statuses.occured_on DESC')
.uniq
Which translates to the SQL:
SELECT DISTINCT users.*
FROM users
INNER JOIN statuses
ON statuses.user_id = users.id
WHERE statuses.status = 'added'
ORDER BY statuses.occured_on DESC
That gives me the error:
PG::Error: ERROR: for SELECT DISTINCT, ORDER BY expressions must appear in select list
LINE 1: ...statuses.status = 'added') ORDER BY statuses.oc...
I'd be happy knowing either the Rails code that would work or the straight SQL.
Also, I'd prefer no sub-selects if possible.
Concider the following database schema change:
StatusTable:
StatusId
Status
UserId
ActiveFrom
ActiveTo
Afterwards you can add additional checks such as:
CONSTRAINT chk_from_to CHECK (ActiveFrom <= ActiveTo)
Then your query would look something like:
SELECT users.*
FROM users
JOIN statuses ON UserId = users.user_id AND ActiveFrom < CURRENT_TIMESTAMP AND ActiveTo > CURRENT_TIMESTAMP
WHERE statuses.Status = 'active'
With such structure you might need to change the way you change statuses, but from my own experience, this structure is much more flexible, and easier to query.
SELECT * FROM users INNER JOIN statuses ON users.id=statuses.user_id WHERE statuses.status='added' ORDER BY statuses.occured_on
After clarification, I don't think the schema is well designed for your goal. Can you clarify why you want the status change history contained in that table? My general approach to this would be that active users should be contained in a table called projects_users, containing project_id, user_id. When they are "removed" they should be removed from that table. Logs of the actions - adding and remove users from projects - should be stored in a separate table.
There's no good way that I'm aware of to write this query given your current design. Even if you fixed the errors, this runs error free in MySQL (which is exactly what you have)
SELECT DISTINCT `users`.* FROM `users`
INNER JOIN `projects_users`
ON `users`.`id`=`projects_users`.`user_id`
WHERE `status`='added'
ORDER BY `projects_users`.`occured_on` DESC
it still won't get you the correct results. The ORDER BY clause will just get you the most recent change to "added", it won't guarantee there is not a more recent "removed" action. To do that you'd need to compare the date of each most recent added record to the date of the most recent removed record, for each user, a nightmare.
I have a Rails application with the following models:
User
Bet
User has many_bets and Bets belongs_to User. Every Bet has a Profitloss value, which states how much the User has won/lost on that Bet.
So to calculate how much a specific User has won overall I cycle through his bets in the following way:
User.bets.sum(:profitloss)
I would like to show the User his ranking compared to all the other Users, which could look something like this:
"Your overall ranking: 37th place"
To do so I need to sum up the overall winnings per User, and find out in which position the current user is.
How do I do that and how to do it, so it don't overload the server :)
Thanks!
You can try something similar to
User.join(:bets).
select("users.id, sum(bets.profitloss) as accumulated").
group("users.id").
order("accumulated DESC")
and then search in the resulting list of "users" (not real users, they have only two meaningful attributes, their ID and a accumulated attribute with the sum), for the one corresponding to the current one.
In any case to get a single user's position, you have to calculate all users' accumulated, but at least this is only one query. Even better, you can store in the user model the accumulated value, and query just it for ranking.
If you have a large number of Users and Bets, you won't be able to compute and sort the global profitloss of each user "on demand", so I suggest that you use a rake task that you schedule regularly (once a day, every hour, etc...)
Add a column position in the User model, get the list of all Users, compute their global profitloss, sort the list of Users with their profitloss, and finally update the position attribute of each User with their position in the list.
Best way to do it is to keep a pre calculated total in your database either on user model itself or on a separate model that has 1:1 relation to user. If you don't do this, you will have to calculate sum for all users at all times in order to get their rating, which means full table operation on bets table. This said, this query will give you desired results, if more than 1 person has the same total, it will count both as rating X:
select id, (select count(h.id) from users u inner join
(select user_id, sum(profitloss) as `total` from bets group by user_id) b2
on b2.user_id = u.id, (select id from users) h inner join
(select user_id, sum(profitloss) as `total` from bets group by user_id) b
on b.user_id = h.id where u.id = 1 and (b.total > b2.total))
as `rating` from users where id = 1;
You will need to plug user.id into query in where id = X
if you add a column to user table to keep track of their total, query is a little simpler, in this example column name is total_profit_loss:
select id, total_profit_loss, (select count(h.username)+1 from users u,
(select username, score from users) h
where id = 1 and (h.total_profit_loss > u.total_profit_loss))
as `rating` from users where id = 1;
Am having a table with quetion_id , nominees and vote_count. In which the values for question_id and nominees are prepopulated from other tables with vote_count as zero.
If the users select some nominees the vote count should be incresed by one. The problem is How to connect the question_id and nominees like for this question_id this nominee is selected .
can some one give example for this situation..
I'll answer based on this scenario:
So you have a...
1) User
who can...
2) Vote
for a...
3) Nominee
And it's a given that MANY users can vote for MANY nominees.
You probably aready have tblUser and tblNominee - so you need a link table that can contain the votes (tblUserNomineeVote).
tblUserNomineeVote has fields for UserId and NomineeId, and therefore registers a vote. You may need to add constraints depending on how many votes a user can register etc.
You can then use:
SELECT
tblNominee.Name,
COUNT(*)
FROM
tblNominee
INNER JOIN
tblUserNomineeVote ON tblUserNomnieeVote.NomineeId = tblNominee.NomineeId
GROUP BY
tblNominee.Name