NEW!! THE KEY TO KEYS: A MATTER OF IDENTITY NEW!!
v.1 (January 2014)
Note:
This paper assumes familiarity with the concepts and terminology introduced in
papers #1, Business Modeling For Database Design and #2, The Costly
Illusion: Normalization, Integrity and Performance, in this series, which
are both recommended as preamble.
If entities in the real world did not have identifiers—attributes
that capture their identity and uniquely identify them—we would not be able to
tell them apart. It follows that an accurate database representation of a
business reality must include keys, R-table columns that formally represent the real
world identifiers in the database.
Keys and kinds thereof, their necessity, selection, function and properties are too often not well known and understood. This paper
Keys and kinds thereof, their necessity, selection, function and properties are too often not well known and understood. This paper
- Defines and explains the key concept;
- Explains the function and properties of the various types of key;
- Describes the criteria for key selection;
- Specifies what is proper DBMS key support;
- Assesses SQL's key support;
- Debunks some common misconceptions about keys.
Table of Contents
1. R-tables and Integrity Constraints
2. Keys and Key Constraints
3. Kinds of Keys
3.1. Natural Keys
3.1.1. Candidate and Primary Keys
3.1.2. Simple and Composite Keys
3.2. Surrogate Keys
4. Key Functions
4.1. Duplicate prevention
4.2. Integrity Burden Reduction
4. 3. View Updatability
5. Foreign Keys and Referential Constraints
6. DBMS Key Support
7. Keys in SQL
7.1. SQL and Duplicates
Appendix A: Duplicate removal in SQL
Appendix B: Duplicates and Language Redundancy
Conclusion
References
2. Keys and Key Constraints
3. Kinds of Keys
3.1. Natural Keys
3.1.1. Candidate and Primary Keys
3.1.2. Simple and Composite Keys
3.2. Surrogate Keys
4. Key Functions
4.1. Duplicate prevention
4.2. Integrity Burden Reduction
4. 3. View Updatability
5. Foreign Keys and Referential Constraints
6. DBMS Key Support
7. Keys in SQL
7.1. SQL and Duplicates
Appendix A: Duplicate removal in SQL
Appendix B: Duplicates and Language Redundancy
Conclusion
References
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