The Key to Keys - Database Design
8 likes1,164 views
Karen Lopez, a data and information architecture expert, emphasizes the importance of keys in data modeling, stating that they are crucial for performance and data quality. She discusses various types of keys and their roles, highlighting the need for standard terminology in the field. The document also addresses the complexities of keys, particularly surrogate keys, and the necessity for data modelers to understand and enforce correct practices.
![IDENTITY/IDENTITY PROPERTY
Issue: How people use them
255
32,767
9,223,372,036,854,775,807
2,147,483,647
IDENTITY [ (seed , increment) ]](https://image.slidesharecdn.com/keytokeysnash-171215000239/85/The-Key-to-Keys-Database-Design-24-320.jpg)
![IDENTITIES
Issue: How people monitor them
IDENTITY [ (seed , increment) ]
AD-322-S](https://image.slidesharecdn.com/keytokeysnash-171215000239/85/The-Key-to-Keys-Database-Design-25-320.jpg)
![WHAT ABOUT SEQUENCES?
CREATE SEQUENCE [schema_name . ] sequence_name
[ AS [ built_in_integer_type | user-defined_integer_type ] ]
[ START WITH <constant> ]
[ INCREMENT BY <constant> ]
[ { MINVALUE [ <constant> ] } | { NOMINVALUE } ]
[ { MAXVALUE
[ <constant> ] } | { NOMAXVALUE } ]
[ CYCLE | { NOCYCLE } ]
[ { CACHE [ <constant> ] } | { NO CACHE } ]
[ ; ]](https://image.slidesharecdn.com/keytokeysnash-171215000239/85/The-Key-to-Keys-Database-Design-27-320.jpg)
![RESTART
ALTER SEQUENCE [schema_name. ] sequence_name
[ RESTART [ WITH <constant> ] ]
[ INCREMENT BY <constant> ]
[ { MINVALUE <constant> } | { NO MINVALUE } ] [ { MAXVALUE <constant> }
| { NO MAXVALUE } ]
[ CYCLE | { NO CYCLE } ] [ { CACHE [ <constant> ] } | { NO CACHE } ]
[ ; ]
AD-322-S](https://image.slidesharecdn.com/keytokeysnash-171215000239/85/The-Key-to-Keys-Database-Design-28-320.jpg)
The Key to Keys - Database Design
- 1. Karen Lopez @datachick #TeamData THE KEY TO KEYS PRIMARY ALTERNATE IDENTITY UNIQUE CLUSTERED SEQUENCE SURROGATE CLUTTERED FOREIGN MEANINGLESS HASH ROWIDENTIFIER ROWID LOOKUP SEARCH PK FK GUID BUSINESS IDENTIFIER PROPERTY CONSTRAINT INDEX
- 3. YES, PLEASE DO TWEET/SHARE TODAY’S EVENT @DATACHICK #TEAMDATA
- 4. KAREN LÓPEZ Karen has 20+ years of data and information architecture experience on large, multi-project programs. She is a frequent speaker on data modeling, data-driven methodologies and pattern data models. She wants you to love your data… She is loves new tech and gadgets
- 5. WHO ARE YOU?
- 6. So many terms and jargon in talking about database stuff
- 8. KAREN SAYS: KEYS 1. Keys are Key to performance AND data quality 2. Concepts can have many ways to implement 3. Not all data modeling vendors use the same terms 4. Not all database vendors use are the same If only there was a profession that specialized in giving thing standard names
- 9. TODAY’S FOCUS Entities and Tables Attributes and Columns Database objects that implement or enforce key- related stuff
- 10. ONE MORE THING… KEYS ARE KEY! Keys (Identifiers) play a role that many modelers & designers forget: They form part of the semantics of our models. Primary keys are used in enforcing constraints on data quality Primary keys are not just about performance.
- 11. Is all about the keys, ‘bout the keys, ‘bout the keys… Depends on understanding the MEANING of the keys and columns Goes all to heck* when you have surrogate keys Depends on the make up of the key parts (columns) NORMALIZATION
- 12. 3NF Every fact is either part of a key or depends upon the key, the whole key, and nothing but the key. ….so help you Codd Michael J Swart
- 13. LINGO, JARGON AND TERMS WE ARE LOUSY AT STANDARDIZING THESE THINGS
- 14. TYPES OF KEY VOCABULARIES Terms used conceptually • Primary key • Alternate key • Composite key • Super key • Candidate key • Surrogate key • … Terms used physically • Primary key • Clustered key • Encryption key • Partitioning key • Index • Identity • Sequence
- 16. AT THE BEGINNING Business Key Logical Key Natural Key
- 17. CLOSER TO DESIGN… Super Key Candidate Key Primary Key Alternate Key Foreign Key
- 18. PRIMARY KEY CRITERIA Applicable to all instances (Mandatory) Unique Stable Small The first two are required by the Relational Model. 3 and 4 required by good practice. But they are not required in data modeling. Modelers should, however, live in the real world most of the time and observe them
- 21. MORE TERMS Surrogate Key Identity Sequence GUID Custom
- 22. SURROGATE KEYS
- 24. IDENTITY/IDENTITY PROPERTY Issue: How people use them 255 32,767 9,223,372,036,854,775,807 2,147,483,647 IDENTITY [ (seed , increment) ]
- 25. IDENTITIES Issue: How people monitor them IDENTITY [ (seed , increment) ] AD-322-S
- 26. HOW DO YOU FIX IT IF IT’S ALREADY GONE OFF? RESEED GAPS Not UNIQUE? Change DataType
- 27. WHAT ABOUT SEQUENCES? CREATE SEQUENCE [schema_name . ] sequence_name [ AS [ built_in_integer_type | user-defined_integer_type ] ] [ START WITH <constant> ] [ INCREMENT BY <constant> ] [ { MINVALUE [ <constant> ] } | { NOMINVALUE } ] [ { MAXVALUE [ <constant> ] } | { NOMAXVALUE } ] [ CYCLE | { NOCYCLE } ] [ { CACHE [ <constant> ] } | { NO CACHE } ] [ ; ]
- 28. RESTART ALTER SEQUENCE [schema_name. ] sequence_name [ RESTART [ WITH <constant> ] ] [ INCREMENT BY <constant> ] [ { MINVALUE <constant> } | { NO MINVALUE } ] [ { MAXVALUE <constant> } | { NO MAXVALUE } ] [ CYCLE | { NO CYCLE } ] [ { CACHE [ <constant> ] } | { NO CACHE } ] [ ; ] AD-322-S
- 29. HOW DO YOU FIX IT IF IT’S ALREADY GONE OFF? RESTART GAPS Not UNIQUE? Change DataType
- 30. HOW DO YOU PREVENT IT? Proper Design Do the math SEED Value Increment Value Use another feature Monitor Max allowable value Max current value Gaps Predict* countdown timer Team Data Script Know your hottest tables Prioritize http://thomaslarock.com/2015/11/sql-server-identity-values-check/
- 31. GUIDS 16 bytes Universally unique Many per table 3F2504E0-4F89-41D3-9A0C-0305E82C3301
- 32. MORE TERMS Numeric Integer BIG Integer Small number
- 35. HOW EASY IS THIS? “Just allocate a surrogate key for every table” Job done. And why do we need data modelers/designers?
- 36. WHAT YOU SHOULD DO: Read Up Ensure you use correct terms Understand how your tools create and generate keys Learn about the Outliers Set the standard for correct term use
- 37. THANK YOU, YOU WERE GREAT. KAREN LOPEZ @DATACHICK