This document contains the notes from a presentation by Gonçalo Chaves on SQL databases. It discusses challenges in database development including lack of SQL knowledge by engineers, poor scalability by novices, and common mistakes made like overuse of views and queries without limits. It provides tips on database design best practices such as normalization, appropriate keys and indexes, data types, handling NULL values correctly, and balancing integrity and performance. Debugging and monitoring tools are also recommended. The importance of documentation, testing, and maintenance is stressed.

1. XII Encontro da comunidade SQLPort

2.  Name: Gonçalo Chaves
 Alias: Chaves
 Job: Senior Analyst
 Company: Viatecla
 Im: evolution69@msn.com
 Tw: @gchaves
 Hobbies: reading, photo, gaming
 Email: gchaves@viatecla.com
 Communities: xamlpt, pontonetpt, sqlport

3. “The biggest problem in databases is
the base data…”

4.  Main challenges
 Why we don’t care
 Analysis and procedures
 Tools
 Use Cases
 References

5.  Engineers knows programing but they don’t
know SQL!

6.  Rookies don’t thing in scalability!

7.  High availability
 Scale and Scale
 Trustful transactions
 Performance and tuning
 Maintenance and archiving
 Partitioning
 Data integrity

8.  The easy path
 Comfort, learning is a painful process
 No professional training
 No time!
 The big truck rule
 Scale and trust aren’t known
 “Microsoft’s lema”

9.  Don’t know the engine
 Wrong Assumptions
 Re-use views, queries, with no limits
 Data type? What? nvarchar don’t fit in all?
 Unknown Transaction Isolation levels
 Tons of locks on a single query

10.  Normalization
 Careful to much can be inefficient
 Appropriate Keys and Indexes
 Right Primary and FK’s
 Choose for relations and integrity

11.  Don’t over on Indexes
 Take’s disk space
 Drop index for bulk insertion
 Some WHERE’s clauses can’t take advantage on ix
 Evaluate and test you ix

12.  Each Database is a Database
 BETWEEN can be more efficient than operators
 Native functions (Convert, format…)
 Aggregate functions (max, min, count, …)

13.  The NULL cancer… you must know NULL well
 ISNull can be a painful
 Wrong assumption on fields
 Null datatype vs “Null”
 Non safe transaction
 Logic looseness

14.  My debug:
 Profiler… yeah it’s heavy but it’s useful!
 TA – tuning advisor
 Activity monitor
 Look for index, keys, fragments,

15.  Daily, every sql dev is also an sql admin!
 RedGate suite
 QueryExpress (light, keep simple)
 TableDiff.exe
 DMVStats (dataware house)
 SQL Server Cache manager

16.  DBA? Where?
 SQL Internals Viewer
 SQLQueryStress (in dev or stage scenarios)
 SQLIO Disk Benchmark tool (on server)

17.  SQL Security
 Roles may be insufficient
 Prevent SQL injection
 Prevent non logic queries that can burn your data
 Remember, it’s more easier broke sql security by
your app than anything else.

18.  The devil ….
SELECT *

19.  Dam accelerators ….
 ADO.NET
 SQLDATASOURCE
 LINQ to SQL
 Entity Framework …

20.  Abuses on
 Group by ; Having; Inner join
 Sub queries with sub queries with …
 #temp_table for everything…
 DML cmd’s
 Constraints for everything…

21.  Good sense
 Know your data 5
 Maintenance 4
 Job your data 3 Frag
 Integrity vs Performance 2 Perf
Disk
1
 The balance is the key
0
Jan Fev Mar April May June

22.  Database – xpto
 1500 tables
 2700 stored procedures
 ~1.5 M transaction per day
 Delete in cascade …
 Broke process
 Restart server

23.  Normalize has needed
 Test your database
 Schedule jobs
 Create Index’s where needed
 Use right tools
 full text search, TA, SSIS

24.  Avoid triggers
 Partitioning
 Archive data
 Data type right usage
 Think in your transaction mode
 Use safe locks
 Test, application stress and faulty

25.  Document you DB 
 Keep scripts in safe
 Update your scripts
 Use facts not assumptions
 Cross your test with others
 Right lock safe usage
 Define db architecture

26.  A good DB start’s on your apps
 Cache is more than welcome
 “The 4 connections challenge..”
 Multiple Environments keep DB’s updated
 Keep your analysis update

27.  Developers exists in C# not in SQL – Deal with it!
 Train your team – code review; sessions; books
 Use the right tools on right scenarios
 Integrity vs Performance
 Keep in mind security concerns
 Make Maintenance plans – from the beginning

28.  Usual blog’s / Communities
 SQL 2008 internals
 Write Smart Sql
 SQL For Smarties
 Sql forums … sqlport 

29.  Thank you all 
 Do right SQL before the pain!
 Follow me at:
http://pontonetpt.org/blogs/chaves
http://xamlpt.com/blogs/chaves
 gchaves@viatecla.com
 www.viatecla.com