SQL Server Error 547 — The statement conflicted with the FOREIGN KEY constraint

The INSERT statement conflicted with the FOREIGN KEY constraint "FK_X". The conflict occurred in database "Y", table "dbo.Z", column 'W'.

You tried to insert/update a row referencing a parent value that doesn't exist, or delete a parent row that child rows still depend on. The same error number also covers CHECK constraint violations, so read the message carefully — it names which constraint fired.

Common causes

• Inserting a child row (e.g. an order) before its parent row (e.g. the customer) exists
• Deleting a parent row without first deleting or reassigning its child rows
• Application inserting foreign keys from stale cached data (the referenced row was deleted since)
• A CHECK constraint rejecting a value outside its allowed range (same error number, different constraint type)

How to fix it

1. Read the message for the exact constraint and column named — it tells you which relationship failed.
2. For inserts: confirm the parent row exists first, or fix insert ordering in the application/transaction.
3. For deletes: either cascade the delete (ON DELETE CASCADE, used carefully) or explicitly remove/reassign child rows first.
4. For CHECK constraint hits: validate the incoming value against the constraint definition (sys.check_constraints) before writing.

Related

• Error 2627 — Primary key violation