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Databases Reporting with SQL Aggregate and Numeric Functions Review: Aggregate and Numeric Functions

Posted by doesitmatter
doesitmatter
12,885 Points

SELECT COUNT(platform) FROM games

There is a question asking what the following line evaluates to:

SELECT COUNT(platform) FROM games;

Since the table has 4 rows, it should be 4. However when I enter this, it says FALSE. How can this be?

1 Answer

andren
andren
28,538 Points
andren
andren
28,538 Points

4 is wrong because 2 of the rows contain NULL, which is the absence of data. NULL is not counted by the COUNT function as a value. So the result of that query would actually be 2.

This behavior was mentioned in the Counting Results lecture at the start of this section of the course.

doesitmatter
doesitmatter
12,885 Points

I forgot that completely, thanks a lot!