Duplicate Key Constraint Violation Error

Specify what to do when a conflict occurs — DO NOTHING or DO UPDATE.

-- Insert or do nothing
INSERT INTO users (id, email, name)
VALUES (1, 'john@example.com', 'John')
ON CONFLICT (email) DO NOTHING;

-- Insert or update (upsert)
INSERT INTO users (id, email, name)
VALUES (1, 'john@example.com', 'John')
ON CONFLICT (email) DO UPDATE
SET name = EXCLUDED.name;

Ignore duplicate key errors silently.

INSERT IGNORE INTO users (id, email, name)
VALUES (1, 'john@example.com', 'John');

Query for duplicates before inserting.

const existing = await db.query(
  "SELECT id FROM users WHERE email = $1",
  [email]
)
if (existing.rows.length > 0) {
  return { error: "Email already registered" }
}
await db.query(
  "INSERT INTO users (email, name) VALUES ($1, $2)",
  [email, name]
)