In Defense of Nulls

Conclusion and References


The vast majority of database users and developers do not have a strong grounding in logic systems. The mismatch between natural language concepts and 2-valued logic can cause as many difficulties as the seemingly unusual nature of 3-valued logic. The gain in expressive power and the simplicity of 3-valued logic justifies its use in database access.

Similarly, nulls have an important role in relational databases. To remove them from the currently flawed SQL implementations would be throwing out the baby with the bath water. On the other hand, the flaws in SQL should be repaired immediately. The changes to SQL's handling of 3-valued logic should have comparatively minor effect on users in the short term and significant improvements to the usability of data in the long term.

Database users and developers should educate themselves on the nature and power of SQL and of relational databases in general. They should always have real SQL/relational expertise on tap for assistance in querying and manipulating the database. The issues raised in this article occur in real world situations much more often than many believe. The users and developers should further demand that their database vendors repair the SQL problems described above and increase their conformity to the relational model. Or they should change to more robust relational implementations.


(1) McGoveran, David. "Nothing from Nothing: Part IV," Database Programming & Design, vol. 7, #3 (March 1994).

(2) Codd, E. F. "Missing Information (Applicable and Inapplicable) in Relational Databases," ACM SIGMOD Record, vol. 15, #4 (1986) and "More Commentary on Missing Information," ACM SIGMOD Record, vol. 15, #5 (1986).

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