Q: Performance

Hello,

Because of daily usage of large tables, I have some performance questions I'd like answers to:

1. What's faster:

   ---

2. select rownum from A where A.field1 NOT IN
   (select fieldA from B)
   
3. select rownum from A where NOT EXISTS
   (select 'x' from B where A.field1 = B.fieldA)
   
4. Anything else
5. Are there performance differences between:

   ---

6. Select count(*) ...
7. Select count(rownum) ...
8. Select count('x') ....
9. What's faster:

   ---

10. Insert into ... values (....) as select ...
11. Insert with a cursor