foreign_key_violation update or delete on table “…” violates foreign key constraint (restrict) — 23503

Symptoms

An UPDATE or DELETE on a referenced (parent) row was blocked because dependent (child) rows still reference it under a RESTRICT/NO ACTION foreign key. PostgreSQL raises SQLSTATE 23503 (foreign_key_violation).

• Deleting/updating a parent row that has children.
• The FK uses RESTRICT or NO ACTION (no cascade).
• The DETAIL line names the referencing table and key.

What the server log shows

ERROR:  update or delete on table "customers" violates foreign key constraint "orders_customer_fk" on table "orders"
DETAIL:  Key (id)=(42) is still referenced from table "orders".

Why PostgreSQL raises this — what the manual says

Section 5.5.5 Foreign Keys:

“RESTRICT is a stricter setting than NO ACTION. It prevents deletion of a referenced row.”

A foreign key with RESTRICT/NO ACTION forbids removing or re-keying a parent row while child rows reference it. Such an operation would orphan the children, so PostgreSQL reports 23503.

Common causes

• Deleting a parent that still has dependent rows.
• Updating a referenced key value with children present.
• Expecting cascade behaviour where the FK uses RESTRICT/NO ACTION.

How to fix it

1. Delete/repoint the child rows first, then the parent.
2. Define the FK with ON DELETE CASCADE/ON UPDATE CASCADE if that’s intended.
3. Use a soft-delete or reassign children before removing the parent.

Related & next steps

• SQLSTATE 23503 — Foreign Key Violation (full reference)
• Message: insert or update violates foreign key constraint
• Glossary: Foreign key

Reference: PostgreSQL 18 Section 5.4 “Constraints”.