1. Query Tuning Fundamentals

2. Vern Rabe Portland, OR independent consultant, trainer
MCTA, MCDBA, MCSE, MCITP
VP Oregon PASS chapter
Working with/focusing on SQL Server since 1993, starting with SQL Server 4.21a

3. What We’ll Cover The Optimizer Tools Query Writing Suggestions
Stored Procedures
Triggers
Views
Indexes

4. The Optimizer What is it? What does it do?
Not all plans considered (Good enough)
Timeout?
Statistics>
Auto update statistics
Auto create statistics

5. Tools What Resource (usually) has Most Performance Impact?
I/O
SET STATISTICS>
SET STATISTICS IO ON
SET STATISTICS TIME ON
Execution Plan
Estimated vs. Actual>
Join types: Merge/Nested Loop/Hash Match
Each has its place
Execution Logging>
“home grown”

6. Query Writing Suggestions
Think set (avoid RBAR)
Sometimes “chunk”
NOLOCK (READUNCOMMITTED)>
Avoid SELECT * in production code
Unnecessary bits across the wire
Plans often not as efficient>
UNION vs. UNION ALL>
Always include schema name
SET NOCOUNT ON

7. Query Writing Suggestions
SARGable>
Watch out for Implicit Conversion>
Avoid leading wild card comparisons
Avoid user defined scalar functions in predicates>
Limit number of JOINs
DISTINCT
Only UPDATE if something changed>

8. Stored Procedures Why stored procedures? Parameter Sniffing>
Code modularity
Pre-compiled
Parameter Sniffing>
WITH RECOMPILE
OPTION (RECOMPILE)
Branch
Do not name a stored procedure “sp_”…

9. Triggers Can cause performance issues
Try to use CONSTRAINT first
Performance issues obfuscated
Triggers code is not in Estimated Execution Plan>

10. Views Views per se are not a performance problem
Abuse of views ARE a performance concern
Views of views – too many joins and obfuscated
Indexed (materialized) views

11. Not sure what should go here
Thanks. Questions?
Not sure what should go here
@VernRabe
Vern Rabe

12. Thanks
Questions?
Contact information
LinkedIn
Resources
Join operators