Job key defaulted to 0 for some new hires

HI All,

I am facing problem for new external hires in my system.

Could you please tell,

1. How job key is created when a new hire in done in the SAP HR system.?

2. There is a group of employees for whom the job key is defaulted to 0 in the system. Please tell what step would the HR missed while hiring, so that the job key is defaulted to 0?

3. Is there a standard report or some way to update the job key manually for multiple employees at the same time.?

Waiting for your quick responses..!!!

Thanks,

Loganathan.