A user wanted to recover a SQL job that had been deleted from the agent. We do backups of MSDB, of course, but how would you actually recover the job definition?

Thanks to ServerFault and user squillman, we used the following technique. Restore a copy of MSDB (we used MSDB_old, in this case). Then run the following script:

DECLARE @JobID UNIQUEIDENTIFIER
SELECT @JobID = job_id FROM msdb_old.dbo.sysjobs WHERE NAME='My Lost Job'

INSERT msdb.dbo.sysjobs
SELECT * FROM msdb_old.dbo.sysjobs
WHERE job_id=@JobID

INSERT msdb.dbo.sysjobsteps
SELECT * FROM msdb_old.dbo.sysjobsteps
WHERE job_id=@JobID

SET IDENTITY_INSERT msdb.dbo.sysjobhistory ON
INSERT msdb.dbo.sysjobhistory
    (instance_id,job_id,step_id,step_name,sql_message_id,sql_severity,
     [message],run_status,run_date,run_time,run_duration,operator_id_emailed,
     operator_id_netsent,operator_id_paged,retries_attempted,[server])
SELECT
    instance_id,job_id,step_id,step_name,sql_message_id,sql_severity,
    [message],run_status,run_date,run_time,run_duration,operator_id_emailed,
    operator_id_netsent,operator_id_paged,retries_attempted,[server]
FROM msdb_old.dbo.sysjobhistory
WHERE job_id=@JobID
SET IDENTITY_INSERT msdb.dbo.sysjobhistory OFF

INSERT msdb.dbo.sysjobschedules
SELECT * FROM msdb_old.dbo.sysjobschedules
WHERE job_id=@JobID

Worked like a charm! Thanks, squillman!
Note that you’d have to alter this script some if you were trying to retrieve an old version of a still existing job (because your job_id would conflict).