SQL Insert with sub-select and multiple rows

Question

I have an existing documents table and a new permissions table. I want to create a script that will give all permissions to all of the existing documents. The documents_permissions table will need the document_id and permission_id (1,2,3). So for each document I will need to insert 3 rows. This is where I am at atm:

INSERT INTO `documents_permissions` (`document_id`, `permission_id`)
SELECT `id`, '1' FROM `documents`

but I'd need to repeat that for each permission. What is the best way to do this?

Answer 1

try this:

USe CROSS JOIN

INSERT INTO `documents_permissions` (`document_id`, `permission_id`)
select  `id`,a.permissions
 from(
select 1 as permissions union all
select 2 union all
select 3 )a
cross join
`documents` d