No way to use TSQL Output with normal foreign key constraints?

Question

The following snippet fails with error:

The target table 'dbo.forn' of the OUTPUT INTO clause cannot be on either side of a (primary key, foreign key) relationship. Found reference constraint 'FK_forn_prim'."

I can only use output by disabling foreign key constraints? How can this be done?

IF OBJECT_ID ('dbo.forn') IS NOT NULL
begin
    alter table dbo.forn drop constraint FK_forn_prim
    DROP TABLE dbo.forn;
end
IF OBJECT_ID ('dbo.prim') IS NOT NULL
    DROP TABLE dbo.prim;
go

CREATE TABLE dbo.prim (c1 int PRIMARY KEY);
CREATE TABLE dbo.forn (c1 int CONSTRAINT FK_forn_prim FOREIGN KEY (c1) REFERENCES dbo.prim(c1));
go

INSERT INTO dbo.prim
    OUTPUT inserted.c1 INTO dbo.forn
SELECT 1;

Answer 1

Normally you output to a table variable or temp table, then use that to insert to the final table.

Answer 2

You're correct, output statements won't work on tables under foreign key constraints.

Another option would be to temporarily disable the constraints while you insert the data. Though this shouldn't be the norm, it works well for one time loads of data.

ALTER TABLE dbo.forn
NOCHECK CONSTRAINT FK_forn_prim
GO

INSERT INTO dbo.prim
    OUTPUT inserted.c1 INTO dbo.forn
SELECT 1;

ALTER TABLE dbo.forn
CHECK CONSTRAINT FK_forn_prim
GO