Actual execution plan vs Estimated execution plan

The benefit of the actual execution plan is that you can see the actual number of rows passing through each step - compared to the estimated number of rows.

But what about the "cost percentages" ?

I believe I've read somewhere that these percentages is still just an estimate and is not based on the real execution.

Does anyone know this and preferable have a link to something that documents it?

ThanksThe cost percentages is what let you know if you need to change table placement in JOINS or use index to improve performance. The information you are looking is in SQL Server Profiler in Management Studio or Enterprise Manager. You use the Profiler to find duration of SQL statements and more. Run a search for Profiler in SQL Server BOL (books online). Hope this helps.