Delete all rows except 10 random rows

Question

Hi,
how can I delete all rows from table JOBS except 10 random rows?
Someone asked it before (not here..): http://stackoverflow.com/questions/10820105/t-sql-delete-except-top-1
but I didn't understand the answer, and I don't think it will work in PL/SQL.
If the answer in StackOverflow does works in PL/SQL, I will glad if someone explains me with better example,
If the answer in StackOverflow does'nt work in PL/SQL, I will glad if someone gives me an example.
thanks!

Answer 1

Actually I found a problem in this solution.
delete from jobs where rowid not in (select rowid from jobs where rownum<=10) ;I used the above code to delete all rows except 10 in JOB_HISTORY table, but for some reason the rows that were chosen were only in the range in which (144<=EMPLOYEE_ID<=146).
I tried this several times and always i stayed with rows in this range.
Here are the queries:
SQL> select employee_id from job_history;
EMPLOYEE_ID
144
144
144
144
144
145
145
146
146
146
146
146
146
146
147
147
147
147
149
149
149
156
156
156
156
156
156
156
158
158
158
158
158
158
158
158
159
159
159
165
165
165
171
171
171
171
46 rows selected
SQL> delete from job_history where rowid not in (select rowid from job_history where rownum <= 15);
31 rows deleted
SQL> select employee_id from job_history;
EMPLOYEE_ID
144
144
144
144
144
145
145
146
146
146
146
146
146
146
147
15 rows selected
SQL>
Glad if someone can explain me why I get this result.
Thanks
Edited by: 998093 on 05:01 05/04/2013