1. Execution plans Eugene Meidinger @sqlgene www.sqlgene.com/powerbi/

2. About me Business Intelligence developer
Worked for All-Lines for 5 years
Spoken at Pittsburgh SQL User Group and various SQL Saturdays
Help lead the Pittsburgh Power BI User Group
Pluralsight Author
Went from SQL newb to SQL pro

3. Why are execution plans important?
They are simple to use
They are key to improving query performance
They give you insight to the database engine

4. What is an execution plan?
Instructions for how to process a query
Can think of it as a recipe
Created by the query optimizer at run time
Execution plans are cached after the first run
Many different ways to process the same query
For trivial queries, a simple plan is used
Can be forced with hints
Don’t try to outsmart the database engine

5. How to view the execution plan?
Go to Query
Click Include Actual Execution Plan
Or, Press Ctrl + M
Or click the execution plan icon on the toolbar

6. What does a plan look like?

7. How to read an execution plan
Read from right to left and top to bottom
Icons represent operators
Operators have cost below them
Arrows represent data flow
Bigger arrows represent more data
Hover over icons and arrows for more detail

8. Reading the Arrows

9. Reading the Popup box
Focus on the top, bottom, cost and estimated versus actual
Top explains the operator
Bottom is the important detail
Est vs. Act can be a problem
The rest isn’t important yet

10. Missing index SQL Server will suggest an index if needed
Use with caution

11. Comparing Queries Query Cost – Relative to Batch
Run multiple queries to compare them

12. Types of operators
Gathering Data
Joining Data
Manipulating Data
MISC

13. Gather data Table scan Clustered index scan Clustered index seek
Nonclustered index scan
Nonclustered index seek
RID lookup
Key lookup

14. Scans and seeks Scan versus seek Clustered versus nonclustered
Scan – Going through all of the rows
Seek – Going to a specific row
Clustered versus nonclustered
Clustered – using the whole table
Nonclustered – taking advantage of the index
Tables versus heaps
Key Lookup – uses the primary key to find a row
RID Lookup – uses the row number in a heap to find a row

15. Joins Merge Join – Joins two sorted datasets
Nested loop join – Loops a small data set over a larger one
Hash join – A hash table is made with the smaller input

16. Manipulate data
Filter
Top
Sort
Compute Scalar

17. Demo

18. SQL Server Execution Plans, 2nd edition

19. SentryOne Plan Explorer