Here is a sample

CREATE TABLE A(ida int PRIMARY KEY);

CREATE TABLE B(idb int PRIMARY KEY, ida int);
ALTER TABLE B 
    ADD CONSTRAINT FK_B_ida FOREIGN KEY (ida) REFERENCES A(ida);

INSERT INTO A (ida) VALUES (1);

INSERT INTO B (idb, ida) VALUES (1, 1);

BEGIN TRANSACTION

UPDATE A 
SET ida = ida + 1000;

UPDATE B 
SET ida = ida + 1000;

COMMIT TRANSACTION;

When running the part between BEGIN TRANSACTION and COMMIT TRANSACTION (all 4 lines), I get an error

Msg 547 - UPDATE instruction conflicts with FOREIGN KEY constraint "FK_B_ida"

In the context of a data migration project (merging 2 dbs with the same schema), I need to mass update primary keys (to avoid collisions) and make sure foreign keys follow.

What is the recommended way to do this?

I was thinking, I could offset keys during copy, but that might make the copy script complex (difficult to avoid listing column names)