1. TSQL Coding Techniques
Are You Playing with Fire?
Mindy Curnutt
TMW Systems / Trimble Navigation

2. About Me Wife & Mother Busy-Bee Musician Soap Making Baking Crocheting
Entrepreneur
Event Planning

3. About Me VP, Information Management, TMW SQL Server MVP
SQL Server since 6.5 / 1995 (20 Years)
SQLPASS Speaker, 2005,
PASS Program Manager 2015 & 2016

4. Agenda
Non-Set Based Approaches Scalar Functions Implicit Conversions Non Parameterized SQL Parameter Sniffing

5. Looping
Cursors
While Loops
Scalar Functions
For / Next…

6. Looping
While Loops
For / Next
Do Until
Cursors

7. How to Not Loop? Think COLUMN instead of ROW
Change many rows with one statement

8. Scalar Functions Simplify your code Code Re-Use
Great - under certain conditions
Under the wrong conditions – can be deadly!

9. How to Use Scalar Functions Safely?
ONLY in Select Clause and with a Small Result Set
Do not reference tables
Not in Where Clause!

10. Implicit Conversions
Who wants to take the time to research and declare the correct data type? BORING
“I tried to think of the most harmless thing. Something I loved from my childhood. Something that could never ever possibly destroy us.”
Cursors
While Loops
For / Next…

11. How to Avoid Implicit Conversions
Correctly define data types
Match data types up
Do not mix data of different types in tables
Know your precision levels
Watch the ORM code

12. Non Parameterized SQL I’ve got a plan. You’ve got a plan too?
Hey, look at that,
We’ve all got our own
SEPARATE PLANS!

13. How to use Parameterization
Do not concatenate SQL parameters as string values
Learn how to use the parameter feature of sp_executeSQL

14. Parameter Sniffing What’s that first value you gave me?
Great, I’ll make you the perfect execution plan for that!
Next time, we don’t have to waste time figuring out a plan, we can use the one I have right here!
Cursors
While Loops
For / Next…

15. How Parameter Sniffing can go awry
Values within a column have very different distribution
Column is naturally increasing at a high rate
Statistics are not accurate
Statistic sampling is not sufficient

16. Value Lists
IN()
CHARINDEX()
Convert to a Table Variable and Join

17. High Performing Value Lists
Convert value list into a Table Variable
Submit value list as a Table Valued Parameter

18. Mindy Curnutt VP, Information Management, TMW Systems
T H A N K Y O U
Mindy Curnutt VP, Information Management, TMW Systems
p: e:
M O V I N G Y O U F O R W A R D