Selecting rows which do not exist for a specific user - sql

Question

I have 4 tables (Users,Config,Fields,AvailableFields)
User's relevant schema is
UserID uniqueidentifier NOT NULL PRIMARY_KEY
Config's relevant schema is
ConfigID uniqueidentifier NOT NULL PRIMARY KEY
UserID uniqueidentifier NOT NULL FOREIGN KEY (User.UserID)
Field's relevant schema is
FieldID uniqueidentifier NOT NULL PRIMARY KEY
AvailableFieldID uniqueidentifier NOT NULL FOREIGN KEY (AvailableFields.AvailableFieldsID)
ConfigID uniqueidentifier NOT NULL FOREIGN KEY (Config.ConfigID)
AvailableFields relevant schema is
AvailableFieldID uniqueidentifier NOT NULL PRIMARY KEY
I am trying to return all of the Available fields for a specific user which they do not have in their Fields table.
Is there a way to do this with a join?
I cannot see a way as the only link between the template AvailableFields table is AvailableFieldID which is a foreign key inside Fields table.

Answer 1

Yes, use the INNER JOIN function with the Config as the first table and Field as the second table to get all users with a Config entry. Then use RIGHT JOIN to select all the available field entries and leave out users with no available field entry.
Then all of the select with WHERE AvailableFields.AvailableFieldID IS NULL. This joins the table with all results from Field/Config table. Then it selects the users who do not have an AvailableFields entry.
Code:
SELECT *
FROM Config
INNER JOIN Field ON Config.ConfigID = Field.ConfigID
RIGHT JOIN AvailableFields ON AvailableFields.AvailableFieldID = Field.AvailableFieldID
WHERE Field.UserID IS NULL
This will return all entries in AvailableFields that don't have a corresponding Field entry (i.e. No users) .

Answer 2

You need to use combination of INNER JOIN and RIGHT JOIN
SELECT af.AvailableFieldID
from Config C
inner join Field F on F.configid = c.configid
right join AvailableFields af on F.AvailableFieldID = af.AvailableFieldID
where f.AvailableFieldID is null

Answer 3

Use
SELECT AvailableFieldID FROM AvailableFields
WHERE AvailableFieldID NOT IN (
SELECT AvailableFieldID from Field f INNER JOIN Config c ON f.ConfigID = c.ConfigID INNER JOIN UserID u on u.UserID = c.UserID
WHERE UserID = "Your condition")
I hope resolve your problem.

Answer 4

I think the most intuitive way would be to use NOT IN with a subquery:
SELECT * from AvailableField
WHERE AvailableField.AvailableFieldId NOT IN
(SELECT AvailableFieldId FROM Field
INNER JOIN Config ON Config.ConfigId = Field.ConfigId
WHERE Config.UserId = ?)
Where ? is a placeholder for the ID of the user you are interested in.
If you are performance-sensitive and are using large tables, multiple joins would be better than this subquery approach.

Answer 5

The simplified version answering your question's requirements:
select af.AvailableFieldID
from AvailableFields af -- all available fields
left join (select distinct f.AvailableFieldID
from Config c
join Fields f
on c.ConfigID = f.ConfigID
where c.UserID = #UserID) AS UserHas -- the fields the user has
on af.AvailableFieldID = UserHas.AvailableFieldID
where UserHas.AvailableFieldID is null -- a field match for the user isn't there
This will also return AvailableFieldID that are not in a Config.
The version you probably want b/c it can be multi-users:
select u.UserID, af.AvailableFieldID
from Users u -- all users
cross join AvailableFields af -- all fields
left join (select distinct f.AvailableFieldID, c.UserID
from Config c
join Fields f
on c.ConfigID = f.ConfigID) AS UserHas -- the fields each user has
on u.UserID = UserHas.UserID
and af.AvailableFieldID = UserHas.AvailableFieldID
where UserHas.AvailableFieldID is null -- a field match for the user isn't there
and (#UserID is null or u.UserID = #UserID) -- option to limit it to one user