Given two queries like:
#users1 = Users.find_by_company_id(2)
#users2 = Users.find_by_office_id(2)
I want to combine the two:
#users_to_show = #users1 + #users2
Issue is how how to prevent duplicate users from showing. Is there a way to combine the two (array?) And then ensure that duplicate records are removed?
Thanks
UPDATED:
# This QUERY gives all of a user's project members, people they work with
#project_ids = #projects.map(&:project_id)
#users = User.find_by_sql [
"SELECT DISTINCT users.*
FROM users
INNER JOIN permissions ON permissions.user_id = users.id
WHERE project_id IN (?) AND permissions.user_id != ?
UNION ALL
SELECT DISTINCT users.*
FROM users
WHERE instance_id = ?",
#project_ids, current_user.id, current_user.instance_id
]
This is a manual SQL approach that may work for you:
#users = User.find_by_sql("
SELECT DISTINCT * FROM USERS WHERE [Place your First complicated where clauses Here]
UNION
SELECT * FROM USERS WHERE instance_id = ?
", current_user.instance_id)
EDIT:
UNION will elimate duplicate records between the two queries.
EDIT: Be sure that each of the queries do not produce duplicates independently. Union will not remove duplicates inside single queries.
Related
I have two tables users and posts and they have association of has_many. I want to fetch details of both users and posts in a single query. I'm able to manage the sql query but I don't want to use the raw query in the code (using execute method) as i think it is kind of simple thing and can be written using active record.
Here is the sql query
SELECT a.id, a.name, a.timestamp, b.id, b.user_id, b.title
FROM users a
INNER JOIN (SELECT id, user_id, title, from, to FROM posts) b on b.user_id = a.id
where id IN ( 1, 2, 3);
I think includes does not help here because i'm dealing with large data.
Can any one help me ?
If you just want those specific columns and nothing else then this will work
User.joins(:post)
.where(id: [1,2,3])
.select("users.id, users.name, users.timestamp,
posts.id as post_id, posts.user_id as post_user_id,
posts.title as post_title")
This will return an ActiveRecord::Relation of User objects with virtual attributes for post_id, post_user_id (Not sure why you need this one since you already selected users.id), and post_title.
The query produced will be
SELECT users.id,
users.name,
users.timestamp,
posts.id as post_id,
posts.user_id as post_user_id,
posts.title as post_title
FROM users
INNER JOIN posts on posts.user_id = users.id
where users.id IN ( 1, 2, 3);
Please note you may have multiple User objects, one for each Post, just as the SQL query does.
You can execute your exact query using the string version of joins e.g.
User.joins("INNER JOIN (SELECT id, user_id, title, from, to FROM posts) b on b.user_id = users.id")
.where(id: [1,2,3])
.select("users.id, users.name, users.timestamp,
b.id as post_id, b.user_id as post_user_id,
b.title as post_title")
Additionally to avoid some of the overhead you can use arel instead e.g.
users_table = User.arel_table
posts_table = Post.arel_table
query = users_table.project(Arel.star)
.join(posts_table)
.on(posts_table[:user_id].eq(users_table[:id]))
.where(users_table[:id].in([1,2,3]))
ActiveRecord::Base.connection.exec_query(query.to_sql)
This will return an ActiveRecord::Result with 2 useful methods columns (the columns selected) and rows. You can convert this to a Hash(#to_hash) but note that any columns with duplicate names (id for instance) will overwrite one another.
You could fix this by specifying the colums you want selected in the project portion. e.g. your current query would be:
query = users_table.project(
users_table[:id],
users_table[:name],
users_table[:timestamp],
posts_table[:id].as('post_id'),
posts_table[:user_id].as('post_user_id'),
posts_table[:title].as('post_title')
).join(posts_table)
.on(posts_table[:user_id].eq(users_table[:id]))
.where(users_table[:id].in([1,2,3]))
ActiveRecord::Base.connection.exec_query(query.to_sql).to_hash
Since none of the names collide now it can be structured into a nice Hash where the keys are the column names and the values or the row value for that record.
users = User.joins(:posts).includes(:posts).where(id: [1, 2, 3])
Will give you all the users with theirs posts.
then you can do whatever you want with them, but to access posts data for first retrieved user
first_user_posts = users.first.posts # this will not make additional DB queries as you used includes and data is already added
We use joins to have INNER JOIN statement in the SQL
We use includes to load all posts in the memory
I have two tables users and posts and they have association of
has_many. I want to fetch details of both users and posts in a single
query.
can be done with includes like
users = User.includes(:posts).where({posts: {user_id: [1,2,3]}})
other is eager_load and preload you can use as per your requirements, for more https://blog.arkency.com/2013/12/rails4-preloading/
I have my records set up as follows
UserKycScanResults: id, user_kyc_scan_id, match_name <- belongs to UserKycScan
UserKycScan: id, user_id, created_at <- belongs to User
User: id, firstname, lastname
I'm trying to write a join so that I can find users' firstname who have a entry in the user_kyc_scans table and user_kyc_scan table entry date is yesterday along with their match_name from user_kyc_scan_results table if present.
I have tried the following
UserKycScanResult.joins("INNER JOIN user_kyc_scans ON user_kyc_scans.id = user_kyc_scan_results.user_kyc_scan_id
INNER JOIN users ON users.id = user_kyc_scans.user_id").where("users.name = '#{submitted_first_name}', user_kyc_scans.created_at = #{Date.yesterday} ")
But this approach doesn't work. Any help would be appreciated.
And joins and where clauses are not working on rails 2
Please give me any solution to sort this out
Thanks.
Your inner joins query are right but in rails 2 we have to pass joins and conditions these way:
UserKycScanResult.all(:joins => "INNER JOIN user_kyc_scans ON user_kyc_scans.id = user_kyc_scan_results.user_kyc_scan_id
INNER JOIN users ON users.id = user_kyc_scans.user_id",
:conditions => ["users.name = ? AND user_kyc_scans.created_at = ?", submitted_first_name, Date.yesterday])
Document for reference: ruby on rails guides
Happy Coding
I am trying to group some records by category and then select all distinct/unique records based on alias column. Here is as far as i got but its not working - it still brings non distinct records.
Location.where("calendar_account_id = ?", current_user.calendar_accounts.first).group(:id,:alias).order("alias ASC").distinct.group_by(&:category)
What am I doing wrong here?
Try this,
Location.select("DISTINCT(alias), *").where("calendar_account_id = ?", current_user.calendar_accounts.first).order("alias ASC").group_by(&:category)
or
Location.where("calendar_account_id = ?", current_user.calendar_accounts.first).group(:alias).order("alias ASC").group_by(&:category)
This is a hard problem to describe but I have Rails query where I join another table and I want to exclude any results where the join table contain one of three conditions.
I have a Device model that relates to a CarUserRole model/record. In that CarUserRole record it will contain one of three :role - "owner", "monitor", "driver". I want to return any results where there is no related CarUserRole record where role: "owner". How would I do that?
This was my first attempt -
Device.joins(:car_user_roles).where('car_user_roles.role = ? OR car_user_roles.role = ? AND car_user_roles.role != ?', 'monitor', 'driver', 'owner')
Here is the sql -
"SELECT \"cars\".* FROM \"cars\" INNER JOIN \"car_user_roles\" ON \"car_user_roles\".\"car_id\" = \"cars\".\"id\" WHERE (car_user_roles.role = 'monitor' OR car_user_roles.role = 'driver' AND car_user_roles.role != 'owner')"
Update
I should mention that a device sometimes has multiple CarUserRole records. A device can have an "owner" and a "driver" CarUserRole. I should also note that they can only have one owner.
Anwser
I ended up going with #Reub's solution via our chat -
where(CarUserRole.where("car_user_roles.car_id = cars.id").where(role: 'owner').exists.not)
Since the car_user_roles table can have multiple records with the same car_id, an inner join can result in the join table having multiple rows for each row in the cars table. So, for a car that has 3 records in the car_user_roles table (monitor, owner and driver), there will be 3 records in the join table (each record having a different role). Your query will filter out the row where the role is owner, but it will match the other two, resulting in that car being returned as a result of your query even though it has a record with role as 'owner'.
Lets first try to form an sql query for the result that you want. We can then convert this into a Rails query.
SELECT * FROM cars WHERE NOT EXISTS (SELECT id FROM car_user_roles WHERE role='owner' AND car_id = cars.id);
The above is sufficient if you want devices which do not have any car_user_role with role as 'owner'. But this can also give you devices which have no corresponding record in car_user_roles. If you want to ensure that the device has at least one record in car_user_roles, you can add the following to the above query.
AND EXISTS (SELECT id FROM car_user_roles WHERE role IN ('monitor', 'driver') AND car_id = cars.id);
Now, we need to convert this into a Rails query.
Device.where(
CarUserRole.where("car_user_roles.car_id = cars.id").where(role: 'owner').exists.not
).where(
CarUserRole.where("car_user_roles.car_id = cars.id").where(role: ['monitor', 'driver']).exists
).all
You could also try the following if your Rails version supports exists?:
Device.joins(:car_user_roles).exists?(role: ['monitor', 'driver']).exists?(role: 'owner').not.select('cars.*').distinct
Select the distinct cars
SELECT DISTINCT (cars.*) FROM cars
Use a LEFT JOIN to pull in the car_user_roles
LEFT JOIN car_user_roles ON cars.id = car_user_roles.car_id
Select only the cars that DO NOT contain an 'owner' car_user_role
WHERE NOT EXISTS(SELECT NULL FROM car_user_roles WHERE cars.id = car_user_roles.car_id AND car_user_roles.role = 'owner')
Select only the cars that DO contain either a 'driver' or 'monitor' car_user_role
AND (car_user_roles.role IN ('driver','monitor'))
Put it all together:
SELECT DISTINCT (cars.*) FROM cars LEFT JOIN car_user_roles ON cars.id = car_user_roles.car_id WHERE NOT EXISTS(SELECT NULL FROM car_user_roles WHERE cars.id = car_user_roles.car_id AND car_user_roles.role = 'owner') AND (car_user_roles.role IN ('driver','monitor'));
Edit:
Execute the query directly from Rails and return only the found object IDs
ActiveRecord::Base.connection.execute(sql).collect { |x| x['id'] }
In my app, users can create galleries that their work may or may not be in. Users have and belong to many Galleries, and each gallery has a 'creator' that is designated by the gallery's user_id field.
So to get the 5 latest galleries a user is in, I can do something like:
included_in = #user.galleries.order('created_at DESC').uniq.first(5)
# SELECT DISTINCT "galleries".* FROM "galleries" INNER JOIN "galleries_users" ON "galleries"."id" = "galleries_users"."gallery_id" WHERE "galleries_users"."user_id" = 10 ORDER BY created_at DESC LIMIT 5
and to get the 5 latest galleries they've created, I can do:
created = Gallery.where(user_id: id).order('created_at DESC').uniq.first(5)
# SELECT DISTINCT "galleries".* FROM "galleries" WHERE "galleries"."user_id" = 10 ORDER BY created_at DESC LIMIT 5
I want to display these two together, so that it's the 5 latest galleries that they've created OR they're in. Something like the equivalent of:
(included_in + created).order('created_at DESC').uniq.first(5)
Does anyone know how to construct an efficient query or post-query loop that does this?
order isn't available, but you can use sort - or sort_by as suggested by jvnill in this answer
As you've stated, you can use the following code:
(included_in + created).sort_by(&:created_at).uniq.first(5)
How about:
Gallery.joins("LEFT JOIN galleries_users ON galleries.id = galleries_users.gallery_id")
.where("galleries_users.user_id = :user_id OR galleries.user_id = :user_id", user_id: id)
.order("galleries.created_at DESC")
.limit(5)
I'm assuming the name of your HABTM join table is galleries_users (which is the default).
Union the two queries and select the order from the union.