Null (SQL): Difference between revisions

Revision as of 14:54, 7 November 2024

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Here <code>AVG(i)</code> is 200 (the average of 150, 200, and 250), while <code>AVG(j)</code> is 150 (the average of 150, 200, 250, and 0). A well-known side effect of this is that in SQL, <code>AVG(z)</code> is not equivalent with not <code>SUM(z)/COUNT(*)</code> but with <code>SUM(z)/COUNT(z)</code>.<ref name="Chamberlin1998"/>

The output of an aggregate function can also be Null. Here is an example: