1. T-SQL gotchas and power-ups
or things that every developer should know
Andrey Nikolov
Software developer at Kodar Ltd.

2. Sponsors

3. About me Software developer at Kodar Ltd.
More than 15 years of experience in developing database applications
Working with SQL Server since version 2000
MCP, 66% MCSA: SQL Server 2012/2014 
KODAR Ltd.
Systems for efficient software
solutions and optimizations
3 |

4. Gotcha vs Power-Up
Gotcha (programming), a counter-intuitive, but documented, behavior in a computer system (as opposed to a bug)
In video games, power-ups are objects that instantly benefit or add extra abilities to the game character

5. Agenda Window(ing) functions and OVER clause
Temp tables vs temp variables
Using SELECT * in a view
Few common mistakes
Scalar UDFs
Object names
Post execution performance analysis
Q&A
5 |

6. Window(ing) functions and OVER clause
OVER Syntax:
OVER ()
OVER (ORDER BY [field name])
OVER (PARTITION BY [field name] ORDER BY [field name])
OVER (PARTITION BY [field name] ORDER BY [field name] ROWS|RANGE …)
CURRENT ROW, UNBOUNDED PRECEDING, UNBOUNDED FOLLOWING
Functions:
ROW_NUMBER
FIRST_VALUE / LAST_VALUE
LAG / LEAD
COUNT / SUM / MIN / MAX
etc.

7. Temp tables vs temp variables
They are NOT in-memory objects
They have different:
Scope
Transactional behavior
Statistics
Indexes
DDL
Parallelism

8. Using SELECT * in a view DEMO
Prevents performance tuning by creating covering indexes
Design view – incorrect aliases
SELECT * was designed for interactive use

9. Few common mistakes UNION IN vs NOT IN ISNUMERIC SET vs SELECT
ORDER BY
MONEY
Aaron Bertrand
Performance / Storage Comparisons : MONEY vs. DECIMAL
(images disappeared few months ago).

10. Scalar UDFs They are convenient for code reuse
Their execution is not visible in actual execution plans
They are executed for each row
They rarely perform well

11. Object names
DEMO

12. Post execution performance analysis
sys.dm_exec_query_stats
sys.dm_exec_sql_text
sys.dm_exec_query_plan
sys.dm_exec_plan_attributes

13. Q&A

14. Sponsors