This is task table:
This is user table:
I want to select user tasks.
I would give from backend ("given_to_user) id.
But The thing is I want that SELECTED data would have usernames instead of Id which is (created_by_user and given_to_user).
SELECTED table would look like this.
Example:
How to achieve what I want?
Or maybe I designed poorly my tables that It is difficult to select data I need? :)
task table has to id values that are foreign keys to user table.
I tried many thinks but couldn't get desired result.
You did not design poorly the tables.
In fact this is common practice to store the ids that reference columns in other tables. You just need to learn to implement joins:
SELECT
task.id, task.title, task.information, user.usename AS created_by, user2.usename AS given_to
FROM
(task INNER JOIN user ON task.created_by_user = user.id)
INNER JOIN user AS user2 ON task.created_by_user = user2.id;
Do you just want two joins?
select t.*, uc.username as created_by_username,
ug.username as given_to_username
from task t left join
users uc
on t.created_by_user = uc.id left join
users ug
on t.given_to_user = ug.id;
This uses left join in case one of the user ids is missing.
Related
I have two tables, Users and Relationships tables. Users table has following columns:
id, name,password,username,email,avatar,followersCount,followingCount,tweetCount.
And the Relationships table has the following columns:
id, followingId, followerId
How should I go about creating a SQL query to extract a user with a specific Id and find id's from Relationships that user is following? So in other words find people that user follows
I've come this far so long
SELECT *
FROM public."Users" JOIN
public."Relationships"
ON (public."Users".id = public."Relationships".id)
If I understand correctly, you want:
SELECT u.*
FROM public."Relationships" r JOIN
public."Users" u
ON u.id = r.followerId
WHERE r.followingId = ?;
? is a parameter placeholder for the user you care about. This returns all the followers of that user.
Do you mean this query
SELECT public."Users".*
FROM public."Users"
JOIN public."Relationships"
ON public."Users".id = public."Relationships".followingId
AND public."Relationships".followerId = a user ID
I am not really clear about followerId and followingId mean but you can change them in the query if it is not what you want.
I am working with an existing database structure (I'm aware the structure might not be perfect, but it is out of my control). I have one table called Users with user id and name among other irrelevant columns.
My problem is with combining users and the table called settlements. The columns in settlements are as following: Case_ID, created_date, approve_date, approving_user_id, control_date, controlling_user_id
How do I interact between the two tables so that my end result shows the names of the ones approving/controlling and not the ID.
I have tried to work with joins but I don't know how to proceed when there are two different users that have approved and controlled.
select
u.user_id, u.agent_name, s.creating_date, s.approving_date,
s.approving_user, s.controlling_date, s.controlling_user
from USERS u
left join SETTLEMENTS s on u.user.id = s.approving_user
I know that I could join them in too two different tables, one called approve and one control but I would prefer to have the end result in the same table.
You want two joins, but you should start with settlements and then bring in the two users tables:
select s.approving_user, s.controlling_date, s.controlling_user,
s.creating_date, s.approving_date,
ua.user_id as approving_user_id, ua.agent_name as approving_agent_name,
uc.user_id as controlling_user_id, uc.agent_name as controlling_agent_name
from settlements s left join
users ua
on ua.user.id = s.approving_user left join
users uc
on uc.user_id = s.controlling_user_id
I'm having trouble doing the following query. The idea is that I have two tables Stores and Users. In Stores I have the columns store_owners and store_last_modified, both values are integer that are related to the id of dbo.Users. How I can display the name that is stored in users related to the two columns. Like that:
select stores.name , users.name as name_store_owner , users.name as name_store_last_modified
from stores
LEFT JOIN users ON stores.store_owners=users.id (related to name_store_owner)
LEFT JOIN users ON stores.store_last_modified=users.id (related to name_store_last_modified)
How do I do that?
Thank you in advance.
You need to give the tables aliases, so you can refer to the same table twice in the from clause. In addition, you need to refer to the right table (users not stores):
select s.name, uo.name as name_store_owner, um.name as name_store_last_modified
from stores s left join
users uo
on s.store_owners = uo.id left join
users um
on s.store_last_modified = um.id
It appears that the condition can be checked without referring the table twice.
select * from
stores s
left join
users u on u.id = s.store_owners
and u.id = s.store_last_modified
From your question it appears that user id (id) should match with both the columns in the stores table for a single row.
I'm building this bartering-type function in this site using PHP/MySQL and I'm trying to create a query that responds with the following fields:
owner's username, title, offerer's username, offerer's item
Basically I have three tables here with the following fields:
users
user_id, username, email
items_available
item_number, owner_id (foreign key that links to user_id), title
offers_open
trade_id, offerers_id (fk of user_id), offerers_item(fk with item_number), receivers_id (fk from user_id)
How do I do this? I've seen some references to many-to-many SQL queries but they don't seem to particularly fit what I'm looking for (for example, the offerers_id and the owner_ids refer to different users_id in the Users table, but how do I make them distinguishable in the sql query?)
If I understand correctly, this is what you are looking for:
SELECT owner.username, oferrers.username, ia.title
FROM offers_open o
INNER JOIN users AS offerers
ON o.offerers_id = offerers.user_id
INNER JOIN items_available AS ia
ON o.offerers_item= ia.item_number
INNER JOIN users AS owner
ON ia.owner_id = owner.user_id
I don't see a title on the users table, so didn't include one.
I'm not sure exactly what output you want, but since your users table will appear twice in the query, they need to be aliased like so:
SELECT offerer.username AS offerer_username, title, receiver.username AS receiver_username
FROM users AS owner
JOIN items_available ON owner_id = owner.user_id
JOIN offers_open ON offerers_item = item_number
JOIN users AS receiver ON receivers_id
Again, don't know if that's what you want, but hope you get the idea.
It sounds as you need an alias of the users table.
Something like?
select
u.*, ia.*, oo.*,u2.*
from
users as u,
items_available as ia,
offers_open as oo,
users as u2
where
u.user_id = ia_user_id and
oo.user_id = u2.user_id and
oo.item_id = ia.item_id
I'm trying to implement something similar to Ruby on Rails' polymorphic relationships.
I have the following three tables :
Events
Users
Organisations
An event can be owner by either a user or an organisation, so my Events table includes the columns: owner_type and owner_id.
I can easily list all events that belong to either users or organisations through an inner join and where clause, however, is there a way to make the join table conditional based on the value of the owner_type column, allowing all events to be listed together, regardless of owner_type?
I hope that makes sense.
Any advice appreciated.
Thanks.
You can't make the join table conditional, so in this case you would have to join events to both users and organisations and use coalesce to merge the common fields (eg. name) together.
select e.id, coalesce(u.name, o.name) owner_name
from events e
left join users u on e.owner_id = u.id and e.owner_type = 'user'
left join organisations o on e.owner_id = o.id and e.owner_type = 'org'
However, you may consider creating an owners table, which contains both users and organisations, with a structure like (id, type, org_id, name, ...). This would only require a single join, but may complicate other areas of your schema, eg. user membership of an organisation.
An alternative method would be to union the users and organisations tables together and then join once from events.
Owner has columns common to all owner-subtypes.
Person and Organization have columns specific to each one.
How about moving ownership information out of Events into two join tables, EventsUsers and EventsOrganisations (each of which has just two columns, FKs to Events and the apppropriate owning-object table) ? Then you can UNION two queries each of which joins through the join table to the owning-object table.
A bit old, but I think it would be useful, this version performs better in my scenario than multiple joins
select e.id,
case when e.owner_type = 'person' then
(
select p.name from person p
where p.id=e.owner_id
)
else
(
select o.name from organization o
where o.id=e.owner_id
)
end entityName,
e.owner_type
from events e
in postgres you could even build a json of entire related entity