insert foreach x where not exists - sql

Question

I have a fairly simple database consisting of three (relevant) tables: users, permissions, and user permissions. The basic premise is simple: when a user gets created, all the records in the permissions table are automatically added to the user_permissions table with a default value. This is all working fine.
However, as I'm currently in development, I continue to add new permissions, which of course existing users won't have since those new permissions didn't exist in the permissions table when they were created. So, I had the brilliant idea to create a little stored procedure to automatically update the user_permissions table with all the permissions not currently existing in the user_permissions table.
So, in short, what I want to do is something like (pseudocode)
For each user without x permission in user_permissions, insert into user_permissions user_id and permission_id
I wasn't quite sure how to do this from an SQL POV. I played with joins and "not exists" but haven't really gotten anywhere.
You can play with my schema here: http://sqlfiddle.com/#!3/b0761/3
Thanks in advance for the help!
EDIT: Schema:
CREATE TABLE users (
user_id int IDENTITY(1, 1) NOT NULL,
user_name varchar(255),
PRIMARY KEY (user_id));
CREATE TABLE permissions (
permission_id int IDENTITY(1, 1) NOT NULL,
permission_name varchar(255) NOT NULL,
PRIMARY KEY (permission_id));
CREATE TABLE user_permissions (
user_id int NOT NULL,
permission_id int NOT NULL,
value tinyint DEFAULT 0 NOT NULL,
PRIMARY KEY (user_id,
permission_id));
ALTER TABLE user_permissions ADD CONSTRAINT FK_user_pe338140
FOREIGN KEY (permission_id)
REFERENCES permissions (permission_id);
ALTER TABLE user_permissions ADD CONSTRAINT FK_user_pe405324
FOREIGN KEY (user_id) REFERENCES users (user_id);
INSERT INTO users(user_name) values('test_username');
INSERT INTO users(user_name) values('test_username2');
INSERT INTO permissions(permission_name) VALUES('permission_1')
INSERT INTO permissions(permission_name) VALUES('permission_2')
INSERT INTO user_permissions(user_id, permission_id, value)
VALUES(1, 1, 1)
INSERT INTO user_permissions(user_id, permission_id, value)
VALUES(2, 1, 1)
EDIT: Query so far
SELECT a.user_id, b.permission_id, 1 as 'value'
FROM USER_PERMISSIONS a right outer join
PERMISSIONS b on a.permission_id = b.permission_id

Answer 1

insert into user_permissions (user_id, permission_id)
select
u.user_id,
p.permission_id
from
users u
cross join permissions p
where
not exists (select 0 from user_permissions with (updlock, holdlock)
where user_id = u.user_id and permission_id = p.permission_id)
Reference: Only inserting a row if it's not already there

Answer 2

INSERT dbo.user_permissions([user_id], permission_id, [value])
SELECT u.[user_id], p.permission_id, 1
FROM dbo.user_permissions AS u
CROSS JOIN dbo.[permissions] AS p
WHERE NOT EXISTS (SELECT 1 FROM dbo.user_permissions
WHERE [user_id] = u.[user_id]
AND permission_id = p.permission_id
)
GROUP BY [user_id], p.permission_id;
As an aside, you should avoid names that tend to require delimiters, e.g. user_id and permissions are keywords/reserved words.

Answer 3

Mansfield,
If I understand you correctly, you want to seed the user_permissions table with a value when you add a new permission.
I'll also assume that you want it to default to 0. After inserting the new permission, running this code will seed the user_permissions table for all users with a default value of 0 for any permissions currently not in use.
--insert into permissions(permission_name) values('newperm');
--select * from permissions
insert into user_permissions(user_id, permission_id, value)
select
u.user_id, p.permission_id, 0
from
users u
cross join permissions p
where
p.permission_id not in(select permission_id from user_permissions)
;
--select * from user_permissions;

Answer 4

The below query will give you the missing userpermission rows to be inserted:
select a.USER_ID,b.permission_id from users a,permissions b,user_permissions c
where c.user_id <>a.user_id and c.permission_id <> b.permission_id