|
Cursor Type |
Work On Table |
Rows retrieve |
Scrolling Type |
SQL Statement |
Fast? |
Read Only? |
Client? |
Server? |
Open Cost |
Fetche Cost |
Scroll Overhaed |
Impact Tempdb |
Concurrency |
Lock |
|
Forward-Only |
directly On table |
Until FETCH |
Only FETCH NEXT |
FAST_FORWARD |
Fast |
Yes |
Yes |
Yes |
Low(not tempdb) |
|
Low |
Low |
Low |
|
|
Static |
Snapshot in Tempdb |
After open cursor |
All scrolling options |
STATIC |
Faster |
Yes |
Yes |
YES |
Highest |
Lowest(create in tempdb) |
|
Highest |
|
No Lock |
|
Keyset-driven |
1.Controlled by Keyset 2.After open cursor,create the keyset of row in the tempdb 3.Limit the membership |
1.First look at the keyset of rows in tempdb. 2.Navigate to table to retrieve the data. |
All scrolling options |
KEYSET |
Slowly |
No,all changes |
NO |
Yes |
lower open cost than the static cursor; Higher open cost than forward-only and dynamic cursors |
Highest |
|
lower impact than the static cursor; higher than forward and dymamic cursor |
|
Higher lock than the static cursor. |
|
Dynamic |
directly On table |
Until FETCH |
All scrolling options,except BSOLUTE |
DYNAMIC |
Slowest |
No,all changes |
NO |
Yes |
Low(not tempdb) than static and keyset cursor |
|
|
|
|
Highest Lock
|
|
Cursor Type |
Update? |
Lock? |
Fast? |
|
Read Only |
No |
No Locks |
fastest |
|
Optimistic |
Yes |
No Locks |
fast |
|
Scroll Locks |
Yes |
U Lock |
Slowest |
