• Save
Microsoft SQL Server Relational Databases and Primary Keys
Upcoming SlideShare
Loading in...5
×
 

Like this? Share it with your network

Share

Microsoft SQL Server Relational Databases and Primary Keys

on

  • 1,649 views

SQL Server guru Ami Levin explains some of the fundamental design principles of relational databases: normalization rules, key selection, and the controversies associated with these issues from a ...

SQL Server guru Ami Levin explains some of the fundamental design principles of relational databases: normalization rules, key selection, and the controversies associated with these issues from a practical perspective.

This presentation hits on the benefits and challenges of using different types of keys - natural, surrogates, artificial, and others.

Each key offers benefits from multiple aspects: data consistency, application development, maintenance, portability and performance.

Ami Levin is a Microsoft MVP and a consultant with SolidQ. Last fall he moved to California from Israel, where he led the Israeli SQL Server User Group.

Statistics

Views

Total Views
1,649
Views on SlideShare
1,649
Embed Views
0

Actions

Likes
5
Downloads
0
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Adobe PDF

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

Microsoft SQL Server Relational Databases and Primary Keys Presentation Transcript

  • 1. Where Are My (Primary) Keys? Ami Levin Mentor, ALevin@SolidQ.com Think Big. Move Fast. Presented to the San Francisco SQL Server User Group September 2013
  • 2. GEOData Database The GEOData database that is used for the demo can be downloaded here: http://sdrv.ms/Z8ZmNb Ami Levin – SolidQ2 |
  • 3. Session Goals Revisit one of the fundamental design principals of relational databases - key selection. Explore the controversies associated with it from a very practical, hands-on perspective, with a special emphasis on some surprising performance issues that may arise from sub- optimal selection of keys... Ami Levin – SolidQ3 |
  • 4. What is a Primary Key? Ami Levin – SolidQ
  • 5. The Forefathers Ami Levin – SolidQ5 |
  • 6. Normalization “A relation whose domains are all simple can be represented in storage by a two-dimensional column homogeneous array of the kind discussed above. Some more complicated data structure is necessary for a relation with one or more non-simple domains. For this reason (and others to be cited below) the possibility of eliminating non-simple domains appears worth investigating. There is, in fact, a very simple elimination procedure, which we shall call normalization” Ami Levin – SolidQ6 |
  • 7. 1st Normal Form  There's no top-to-bottom or left-to-right ordering to the rows and columns  There are no duplicate rows  Every row-column intersection contains exactly one value  There are no repeating groups  All columns are regular Ami Levin – SolidQ7 |
  • 8. 1st Normal Form Ami Levin – SolidQ8 | SSN Name PhoneNumber 123-45-6789 MuammarGaddafi +218-00-9876 987-65-4321 Bashar Assad +1-202-6543221 SSN First Name Last Name PhoneNumber 123-45-6789 Muammar Gaddafi +218-00-9876, +218-00-8765 987-65-4321 Bashar Assad +1-202-6543221 SSN First Name Last Name PhoneNumber1 PhoneNumber2 123-45-6789 Muammar Gaddafi +218-00-9876 +218-00-8765 987-65-4321 Bashar Assad +1-202-6543221
  • 9. 2nd Normal Form  R is in 1NF.  Given any candidate key K and any attribute A that is not a constituent of a candidate key, A depends upon the whole of K rather than just a part of it. Ami Levin – SolidQ9 |
  • 10. 2nd Normal Form Ami Levin – SolidQ10 | Order ID Line Number Customer 0001 1 FISSA 0001 2 FISSA 0002 1 PARIS OrderDetailID OrderID LineNumber Customer AC934245FF00B 0001 1 FISSA 8BA50CC2044AF 0001 2 FISSA F00B344923AB4 0002 1 PARIS
  • 11. 3rd Normal Form  R is in second normal form (2NF)  Every non-prime attribute of R is non-transitively dependent on every candidate key of R. A non-prime attribute of R is an attribute that does not belong to any candidate key of R. A transitive dependency is a functional dependency in which X → Z (X determines Z) indirectly, by virtue of X → Y and Y → Z. Ami Levin – SolidQ11 |
  • 12. 3rd Normal Form Ami Levin – SolidQ12 | Order ID Line Number Product Manufacturer 0001 1 Chair IKEA 0001 2 Gum Mentos 0002 1 Fighter Jet Boeing
  • 13. Keys  Simple  Composite  Candidate  Primary  Artificial / Surrogate  Intelligent  Natural Ami Levin – SolidQ13 |
  • 14. The Debate To ID or not to ID?  IDENTITY (1,1) vs. Natural key Ami Levin – SolidQ14 |
  • 15. Pro Artificial (I) In some cases, no natural key exists and an artificial key is the only option.  Examples? Ami Levin – SolidQ15 |
  • 16. Pro Artificial (II) Natural keys can change. Artificial keys never change.  How Often?  Cascading referential constraints  Artificial keys can change Ami Levin – SolidQ16 |
  • 17. Pro Artificial (III) Natural keys may be long and complex.  Become longer with each level  900 Bytes limit in SQL Server  Multi-column joins Ami Levin – SolidQ17 |
  • 18. Pro Artificial (IX) Artificial keys help improve performance.  Simpler join predicates  Ever increasing clustering effect  Short keys = Smaller DB = Faster Ami Levin – SolidQ18 |
  • 19. Pro Artificial (X) Artificial keys reduce clustered index fragmentation.  Minimize maintenance down time  What about deletes?  What about non-clustered indexes? Ami Levin – SolidQ19 |
  • 20. Pro Natural (I) Natural keys have business meaning.  Artificial keys are never queried for Ami Levin – SolidQ20 |
  • 21. Pro Natural (II) Queries on tables using natural keys require fewer joins.  The more familiar and meaningful the key, the less joins are required  “Bypass” joins Ami Levin – SolidQ21 |
  • 22. Pro Natural (III) Data consistency is maintained explicitly when using natural keys.  Artificial keys enable logical duplicates Ami Levin – SolidQ22 |
  • 23. Pro Natural (IX) Natural keys eliminate potential physical clustering performance issues.  Contention for clustered regions Ami Levin – SolidQ23 |
  • 24. Less Mentioned Issues (I) Artificial keys are the de-facto standard.  ORMs generate artificial keys  LINQ doesn’t cache composite key rows  … Ami Levin – SolidQ24 |
  • 25. Less Mentioned Issues (II) Data statistics and optimizations.  Statistics on artificial keys are useless for parameter sniffing  Estimations on composite key statistics are less accurate Ami Levin – SolidQ25 |
  • 26. Less Mentioned Issues (III) Modularity and portability.  Migration to other platforms  Merging with other databases Ami Levin – SolidQ26 |
  • 27. Less Mentioned Issues (IX) Simplicity and aesthetics. Ami Levin – SolidQ27 |
  • 28. Demo Spec A database of web sites.  URL  Country and city of owner  Country ISO code for external app  Data consistency is crucial Ami Levin – SolidQ28 |
  • 29. Natural vs. Artificial Keys Ami Levin – SolidQ29 |
  • 30. Ask Yourself  Is there a natural key that I can use as a primary key?  Are there a few natural candidates?  Which one is the simplest and most familiar?  How stable is it?  How will it be used logically?  What will be the physical access patterns for this table?  What are the common query types for this table? Ami Levin – SolidQ30 |
  • 31. For More Information  A Relational Model of Data for Large Shared Data Banks (E.F. CODD)  The Relational Model for Database Management: Version 2 (E.F. Codd)  An introduction to database systems (C.J. Date)  Database in Depth: Relational Theory for Practitioners (C.J. Date)  The Database Relational Model: A Retrospective Review and Analysis (C.J. Date)  Joe Celko's Data and Databases: Concepts in Practice (J. Celko)  Joe Celko's SQL for Smarties, Fourth Edition: Advanced SQL Programming (J. Celko)  Database Modeling and Design, Fifth Edition: Logical Design (T.J. Teorey, S.S. Lightstone, T. Nadeau, and H.V. Jagadish)  Pro SQL Server 2008 Relational Database Design and Implementation (L. Davidson, K. Kline, S. Klein, and K. Windisch) Ami Levin – SolidQ31 |
  • 32. WhereAre My Keys? Ami Levin – SolidQ32 |