1. Evil

4. Surrogate
Key
Abuse

5. SSSKA
Society to Stop
Surrogate
Key Abuse

6. Key = a unique predicate
which identifies a tuple
SSSKA

7. Key
room 204
date 2009-04-17
SSSKA

8. Surrogate Key = an
arbitrary unique ID value
added to a tuple, unrelated
to tuple contents
SSSKA

9. Surrogate Key
ID 44906
room 204
date 2009-04-17
SSSKA

10. Surrogate Key Abuse =
misuse of surrogate keys
in a way which harms
your data
SSSKA

11. Primary Key =
meaningless
implementation detail
SSSKA

12. SSSKA

13. SSSKA

14. SSSKA

15. SSSKA

16. SSSKA

17. SSSKA

18. Forms of Abuse
● No real key
● Unnecessary surrogate
keys
● Swapping keys
SSSKA

19. Forms of Abuse
● No real key
● Unnecessary surrogate
keys
● Swapping keys
● ObjectIDs (and UUIDs)
SSSKA

20. Excuses
● "It's standard"
● "There isn't a good key"
● "My framework requires it."
● "Keys shouldn't change"
SSSKA

21. Excuses
● "It's standard"
wrong. SKs not in relational model
● "There isn't a good key"
no, you just don't know what it is
● "My framework requires it."
get a better framework
● "Keys shouldn't change"
what's CASCADE for then?
SSSKA

22. Excuses
"Performance"
SSSKA

23. Excuses
premature optimization
= doing things for
"performance" which you
haven't tested
SSSKA

24. Excuses
premature optimization
generally harms actual
performance
SSSKA

25. Avoid S.K.A.!
● Make sure all relations have real keys
● Use natural keys where you can
● Avoid premature optimization
SSSKA

26. If You Really Loved
Your Data, You
Wouldn't Abuse Keys.
SSSKA

27. SSSKA
Learn More about S.K.A.:
http://it.toolbox.com/blogs/database-
soup/primary-keyvil-part-i-7327
(google "primary keyvil")
This talk is copyright 2009 Josh Berkus, and is licensed under the creative commons attribution license