ORDER BY decode(job,'Clerk',1, 'President',2, 'Analyst',3, 'Salesman',4,'Manager',5,6)

might be what you are looking for.

Be wary of using this sort of construct though - if the jobs change, then you will have to recode any select statements that use it. I have included a default value of 6 so that any jobs that are not listed in the decode will appear at the end of the sort.

It might be better to have a jobs table, and replace the job name in your table with a job id that refers to jobs. Then you could have a sort priority column in the jobs table, and use that to order your results. This means that if jobs are added, the sort order can be changed without recoding anything.