Null (SQL): Difference between revisions

Revision as of 19:05, 13 March 2023

Revision as of 15:50, 1 July 2023

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The Boolean type has been subject of criticism, particularly because of the mandated behavior of the UNKNOWN literal, which is never equal to itself because of the identification with NULL.<ref name="Prigmore2007">{{cite book|author=Martyn Prigmore|title=Introduction to Databases With Web Applications|url=https://books.google.com/books?id=PKggKqIZnN0C&pg=PA197|year=2007|publisher=Pearson Education Canada|isbn=978-0-321-26359-9|page=197}}</ref>

As discussed above, in the [[PostgreSQL]] implementation of [[SQL]], Null is used to represent all UNKNOWN results, including the UNKNOWN BOOLEAN. PostgreSQL does not implement the UNKNOWN literal (although it does implement the IS UNKNOWN operator, which is an orthogonal feature.) Most other major vendors do not support the Boolean type (as defined in T031) as of 2012.<ref>Troels Arvin, [http://troels.arvin.dk/db/rdbms/#data_types-boolean Survey of BOOLEAN data type implementation]</ref> The procedural part of Oracle's [[PL/SQL]] however supports BOOLEAN however variables; these can also be assigned NULL and the value is considered the same as UNKNOWN.<ref name="FeuersteinPribyl2009">{{cite book|author1=Steven Feuerstein|author2=Bill Pribyl|title=Oracle PL/SQL Programming|year=2009|publisher=O'Reilly Media, Inc.|isbn=978-0-596-51446-4|pages=74, 91}}</ref>

==Controversy==