OracleORA-00001

ORA-00001: Unique Constraint Violated

ORA-00001 is Oracle's error for a UNIQUE or PRIMARY KEY constraint violation. It is raised when an INSERT or UPDATE would produce a duplicate value in a unique-constrained column.

Example Query

INSERT INTO employees (employee_id, name)
VALUES (100, 'Alice');
-- Fails if employee_id 100 already exists

Common Causes

  1. 1Inserting a row with a manually specified primary key that already exists
  2. 2Sequence not reset after a bulk data load
  3. 3Parallel sessions inserting the same value simultaneously

How to Fix It

Use a sequence for primary keys: employee_id_seq.NEXTVAL. Handle conflicts with MERGE (upsert). Reset sequences after bulk imports: ALTER SEQUENCE seq INCREMENT BY n; SELECT seq.NEXTVAL FROM dual; ALTER SEQUENCE seq INCREMENT BY 1;

Need a reliable database?

Try Supabase — free PostgreSQL with a generous free tier. No credit card required.

Get started free →

Got a query causing this error?

Paste it into SQLbuddy and get an instant plain-English explanation with optimization tips.

Analyze My Query →
← Browse all SQL errors