23001ERRORTier 2 — Caution✅ HIGH confidence

restrict violation

Category: Integrity Constraint ViolationVersions: All Postgres versions

What this means

SQLSTATE 23001 is raised when a DELETE or UPDATE is blocked by a RESTRICT foreign key constraint — a child row still references the row being deleted or updated in the parent table.

Why it happens

1Deleting or updating a parent row that has child rows referencing it under a RESTRICT foreign key

How to reproduce

Deleting a parent row with existing child references.

trigger — this will ERROR

DELETE FROM departments WHERE id = 1;
-- employees table has rows referencing department_id = 1 with ON DELETE RESTRICT

ERROR: update or delete on table "departments" violates foreign key constraint "employees_department_id_fkey" on table "employees"

Fix 1: Delete child rows first, then delete the parent

When cascading deletion is appropriate.

fix

DELETE FROM employees WHERE department_id = 1;
DELETE FROM departments WHERE id = 1;

Why this works

Removing dependent rows before the parent satisfies the RESTRICT constraint.

Fix 2: Change the foreign key to ON DELETE CASCADE

When child rows should be automatically deleted with the parent.

fix

ALTER TABLE employees
  DROP CONSTRAINT employees_department_id_fkey,
  ADD CONSTRAINT employees_department_id_fkey
    FOREIGN KEY (department_id) REFERENCES departments(id) ON DELETE CASCADE;

Why this works

CASCADE automatically deletes child rows when the parent is deleted, eliminating the RESTRICT error.

What not to do

✗

Drop the foreign key constraint to allow the delete

Why it's wrong: Removing the constraint leaves orphaned child rows with invalid references, corrupting referential integrity.

Sources

📚 Official docs: https://www.postgresql.org/docs/current/errcodes-appendix.html

🔧 Source ref: Class 23 — Integrity Constraint Violation

Confidence assessment

✅ HIGH confidence

Standard SQLSTATE for RESTRICT foreign key violations. Stable across all versions.