Re: Foreign Key constraint fails

[Peter Brawley]

REPLACE INTO, a dubious MySQL extension for exactly the reason you tripped over.

When REPLACE INTO encounters an existing PK it's replacing, it deletes that row. The existence of FK references to your key prevents that (as it must, otherwise such references would be useless).

Your problematic REPLACE should be an UPDATE of the contact. And generally, where there are FKs, safer practice is to stick with INSERT and UPDATE.