In the above post I've illustrated how Composable DML feature can be applied for simultaneous insert to parent child tables. I was trying to use this feature in a similar scenario when I discovered something. The scenario can be depicted as below
CREATE TABLE Parent
ID int IDENTITY(1,1) NOT NULL,
CREATE TABLE Child
( ID int IDENTITY(1,1) NOT NULL,
Parent_ID int REFERENCES Parent(ID),
Now see what happens when you apply the Composable DML feature here
CREATE PROC InsertParentChild
INSERT INTO Child
INSERT INTO Parent (Value1)
Compiling the above proc gives you this error
The target table 'dbo.Child' of the OUTPUT INTO clause cannot be on either side of a (primary key, foreign key) relationship.
Thus you can find that Composable DML cant be applied on table if it forms part of foreign key constraint.