Tuning T-SQL - Professional SQL Server 2005 Performance Tuning - page 244

Finally, you can click the Include Actual Query Plan button on the toolbar (see Figure 9-3).

Figure 9-3

Figure 9-4 shows a typical query plan.

Figure 9-4

Note that execution plans cannot be generated for encrypted stored procedures, triggers,orifyourstored
procedure makes use of temporary tables.

Query Plan Essentials
Now that you've generated a plan, there is a lot to take in. First, know that graphical query plans are read
right to left, and generally bottom to top. Thus, the top-left step is the last step in the plan.

Here are a few things to keep in mind when looking at a graphical plan:

❑ Each step in the plan will be indicated by an icon. These icons have very specific meanings. The

following section contains the entire list of possible icons.

❑ Each step in the plan will receive a cost expressed as a percentage.

❑ The query plan will show an execution plan for every statement in the query pane. These plans

will be listed sequentially in the result pane. Each plan will have a cost relative to the batch. This
is expressed as a percentage.

❑ The steps are connected by arrows showing the order taken by the query when it was executed.

❑ Hovering the mouse over any of the steps shows a pop-up information box giving detailed infor-

mation about the specific step.