23505 — Unique Violation

Nguyên nhân gây ra lỗi này

The value already exists in a column with a UNIQUE constraint or PRIMARY KEY.

Cách sửa

Use INSERT ... ON CONFLICT (PostgreSQL) or ON DUPLICATE KEY UPDATE (MySQL). Check for duplicates before inserting.

-- unique_violation
INSERT INTO users (email) VALUES ('dup@test.com');
-- Fix: use ON CONFLICT
INSERT INTO users (email) VALUES ('dup@test.com')
  ON CONFLICT (email) DO UPDATE SET updated_at = NOW();