I'm trying to create a query that will fetch results from table parties. This table contains two foreign keys and I'm having trouble "mapping" these foreign keys.
For the first foreign key I need to map my host_id column to the actual name of the person users.name.
I was able to solve this with:
SELECT parties.*, users.name as host_name
FROM parties
INNER JOIN users ON parties.host_id = users.id
My second foreign key is to a table called guests which has a FK named party_refer which refers to parties.id.
The following query includes my Guests as part of the results (by appending all of my guests table columns in the results)
SELECT parties.*, users.name as host_name, guests.*
FROM parties
INNER JOIN users ON parties.host_id = users.id
INNER JOIN guests ON parties.id = guests.party_refer
I would like to modify this second INNER JOIN so that the results of (select * from guests) are returned as a single Column called Guests with the results expressed as a JSON.
I believe I need to use array_to_json(array_agg(row_to_json())) but I've been trying for hours to get it working with no luck.
I think you are looking for
SELECT parties.*, users.name as host_name, json_agg(row_to_json(guests)) as guests
FROM parties
INNER JOIN users ON parties.host_id = users.id
INNER JOIN guests ON parties.id = guests.party_refer
GROUP BY parties.id, users.name
Although a subquery may be simpler than extensive grouping:
SELECT
parties.*,
users.name as host_name,
(SELECT json_agg(row_to_json(guests))
FROM guests
WHERE guests.party_refer = parties.id) as guests
FROM parties
INNER JOIN users ON parties.host_id = users.id
(online demo)
You might prefer an explicit json_build_object instead of the row_to_json, e.g.
json_agg(json_build_object('guestName', guests.name))
Related
-- 2. In one table, show how many private topics, admins, and standard users each organization has.
SELECT organizations.name, COUNT(topics.privacy) AS private_topic, COUNT(users.type) AS user_admin, COUNT(users.type) AS user_standard
FROM organizations
LEFT JOIN topics
ON organizations.id=topics.org_id
AND topics.privacy='private'
LEFT JOIN users
ON users.org_id=organizations.id
AND users.type='admin'
LEFT JOIN users
ON users.org_id=organizations.id
AND users.type='standard'
GROUP BY organizations.name
;
org_id is the foreign key that reals both the users table and topics table. It keeps giving me the wrong result by only either counting the number of admins or standard users and putting that for all rows in the each column. Any help is really appreciated as I have been stuck on this for a while now!
So, I am getting an error when I do as you said which is that the users table cannot be specified more than once. I updated the code to how you said to write it but still nothing. They really don't give me any sample data either but I just made some queries and saw the number of times there are private topics for example, which is in the privacy column of the topics table. When I dont get this error as I said, the joins seem to overwrite themselves where each row for all the columns is the same as the last join.
It appears to me that topics and users have no relationship. You're just trying to get the result together in a single query. There are other and possibly better ways to accomplish that but I think this will fix what you've got already (assuming you have id columns for each table.)
SELECT
organizations.name,
COUNT(DISTINCT topics.id) AS private_topic,
COUNT(DISTINCT users.id) FILTER (WHERE users.type = 'admin') AS user_admin,
COUNT(DISTINCT users.id) FILTER (WHERE users.type = 'standard') AS user_standard`
FROM organizations
LEFT JOIN topics
ON organizations.id = topics.org_id AND topics.privacy = 'private'
LEFT JOIN users
ON users.org_id = organizations.id
GROUP BY organizations.name;
I propose this as a more straightforward way:
SELECT
min(o.name) as "name",
(
select count(*) from topics t
where t.org_id = o.id AND t.privacy = 'private'
) as private_topics,
(
select count(*) from users u
where u.org_id = o.id and u.type = 'admin'
) AS user_admin,
(
select count(*) from users u
where u.org_id = o.id and u.type = 'standard'
) AS user_standard
FROM organizations o
GROUP BY o.id;
I have the following tables:
Users
Conversations
Group_Members
I need to select all the conversations where a user with a specific ID takes part in. Users and Group_Members are in a many-to-many relationship.
Why does the following query create duplicate rows on the last select, as seen in this image?
select * from Conversations
select * from Group_Members
select Conversations.*
from Conversations
inner join Group_Members on Group_Members.userid=1054
User.Id and Conversation.Id are primary keys.
Sure, select distinct would work, but I don't understand why the select above creates duplicates.
Your join criteria is wrong. It would join them when it sees a Group_members.userId = 1054 regardless what conversations has. You used your "filter criteria" as your "relation criteria".
Your joining key is in fact ConversationId, and what you used is the filtering.
You should write that as:
select Conversations.*
from Conversations
inner join Group_Members on Group_Members.ConversationId = Conversations.Id
where Group_Members.userid=1054
-- and ConversationId = 4; -- if you would filter for a particular conversation
My users table has the columns
user_id, email
My invites table has the columns
invite_id request_id user_id sent_time
When I run the following query, I get the two tables joined into 1, which is expected.
'SELECT * FROM users INNER JOIN invites ON users.user_id = invites.user_id'
However, when I run the following query,
'SELECT user_id FROM users INNER JOIN invites ON users.user_id = invites.user_id'
I get the following error
OperationalError: (sqlite3.OperationalError) ambiguous column name: user_id [SQL: 'SELECT user_id FROM users INNER JOIN invites ON users.user_id = invites.user_id']
Any help appreciated.
I think the message is pretty clear. SQLite doesn't know what table user_id is coming from.
One simple solution is to qualify the column name usinga table alias:
SELECT u.user_id
FROM users u INNER JOIN
invites i
ON u.user_id = i.user_id;
Another method is to use USING rather than ON:
SELECT user_id
FROM users u INNER JOIN
invites i
USING (user_id);
You need to qualify the column name with table name like below cause both table involved in query have the same column name
SELECT `users`.user_id
FROM users
INNER JOIN invites ON `users`.user_id = invites.user_id
This means you need to be specific about which user_id column you want to display. Even though they're joined that doesn't guarantee they're identical. Some types of joins allow NULL values on one side of the match (e.g. LEFT JOIN), so you need to ask for a particular value:
SELECT users.user_id FROM users INNER JOIN invites ON users.user_id = invites.user_id
I've got 3 tables that look vaguely like this:
Users
----------
UserID
Name
Phone
User Groups
-----------
GroupID
Activity
Group Membership
---------------
UserID
GroupID
Independent Actives
-------------------
UserID
Activity
The idea is that a user can perform an activity either as part of a group or on their own. What I want to do is return all the people that partake in a certain activity. What I have been able to write so far lets me return all the users which are in groups that undertake that activity. What I want to add to this is the ability to see the people that do the activity independently. This is what I have so far:
SELECT
users.name, users.phone, user_groups.activity
FROM users
INNER JOIN group_membership ON group_membership.userID = users.userID
INNER JOIN user_groups ON user_groups.groupID = group_membership.groupID
WHERE user_groups.activity = 'Knitting';
The above bit works fine and it shows all of the users that are part of groups that do knitting, but I also want it to show all the users that are knitting independently. This is what I have attempted to add:
SELECT
users.name, users.phone, user_groups.activity
FROM users
INNER JOIN group_membership ON group_membership.userID = users.userID
INNER JOIN user_groups ON user_groups.groupID = group_membership.groupID
INNER JOIN independent_activity ON independent_activity.userID = users.userID
WHERE user_groups.activity = 'Knitting' OR independent_activity.activity = 'Knitting';
The problem here is the syntax, I understand the algorithm that I'm trying to do but I don't know how to transfer it into sql and so any help is appreciated.
You could use a UNION in this case
SELECT users.NAME
,users.phone
,user_groups.activity
FROM users
INNER JOIN group_membership ON group_membership.userID = users.userID
INNER JOIN user_groups ON user_groups.groupID = group_membership.groupID
WHERE user_groups.activity = 'Knitting'
UNION
SELECT users.NAME
,users.phone
,independent_activity.activity
FROM users
INNER JOIN independent_activity ON independent_activity.userID = users.userID
WHERE independent_activity.activity = 'Knitting';
You also might want to lookup the differences between a UNION and a UNION ALL and decide the one that suites your requirement.
You've got a working answer from SoulTrain. However, for completeness sake I'd like to mention that you don't have to join all those tables. (You could use outer joins here and remove duplicate matches with DISTINCT, but that's not necessary. You don't have to query the users table twice either. And you don't need UNION for doing the distinct job.)
Simply select from the one table you want to display data from, i.e. the users table, and then use EXISTS or IN to get only those users that are either in one set or another.
select name, phone
from users
where userid in
(
select userid
from independent_actives
where activity = 'Knitting'
)
or userid
(
select userid
from group_membership
where groupid in (select groupid from user_groups where activity = 'Knitting')
)
I have a workorder system using SQL Express 2008. I have a table called Workorders that has several personnel that are linked to it via UserID. In the Workorder table I have TechID for the Technician, CustomerID for the Customer, QAID for quality assurance. These are linked back to the User Table via UserID (User Table PK). I want to join the tables to return Technician Name, Customer Name, and QA Name from the User Table and other job information information from the Workorder Table. I have no idea how to construct the join.
What about something a bit like this :
select tech.name as tech_name,
customer.name as customer_name,
qa.name as qa_name
from Workorders
inner join User as tech on tech.userId = Workorders.techId
inner join User as customer on customer.useId = Workorders.CustomerId
inner join User as qa on qa.useId = Workorders.QAID
(Might need some tunning, but the idea should be here)
ie, you are :
starting with a workorder
inner join on its tech guy (a User),
and then inner joinning on its customer (another user)
and so on
And this allows you to get each name, using the right alias in the select clause.
Note that I used aliases in the select clause too -- that might be usefull to have "worker_name" and "tech_name", instead of just two columns names "name" -- especially if you are calling this query from some other programming language.
Note : if one of those userId field can be NULL, you might want to use a left join, instead of an inner join.
select tus.Name as 'TechnicianName',
cus.Name as 'CustomerName',
qus.Name as 'QaName',
wod.*
from WorkOrders wod
left outer join
Users tus on tus.UserId = wod.TechId
left outer join
Users cus on cus.UserId = wod.CustomerId
left outer join
Users qus on qus.UserId = wod.QaId