-- Migración: tabla de relación usuario ↔ empresa(s)
-- Permite asignar uno o varios usuarios a una o varias empresas

CREATE TABLE IF NOT EXISTS user_companies (
  user_id    INT NOT NULL,
  company_id INT NOT NULL,
  PRIMARY KEY (user_id, company_id),
  CONSTRAINT fk_uc_user    FOREIGN KEY (user_id)    REFERENCES users(id)     ON DELETE CASCADE,
  CONSTRAINT fk_uc_company FOREIGN KEY (company_id) REFERENCES companies(id) ON DELETE CASCADE
);