To be clear, I'm not proposing that the company and employee numbers be concatenated into a single column: I'm saying you could have a composite key, comprising

To be clear, I'm not proposing that the company and employee numbers be concatenated into a single column: I'm saying you could have a composite key, comprising the company number column and the employee payroll number column. This would still be a natural key: each component has a meaning outside the system (company numbers appear on company filings and other formal documentation, employee payroll numbers appear on payslips and are communicated to the tax authorities), and the two in combination have a clear business meaning. Of course, you may still want to use a surrogate key for performance or security or other technical reasons, as the article describes. I just wasn't clear on how the specific scenario you laid out made any additional case for their use.