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

Posted by jaesonshin
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jaesonshin
Python Development Techdegree Graduate 9,939 Points

Possible Wrong Answer?

image

What is the result you should expect from the following query?

SELECT COUNT(platform) FROM games;

Hi, Isn't the answer to this question 4? I've chosen 4 and it said I'm wrong. If it isn't could you tell me why?

regards,

Jaeson

2 Answers

Jennifer Nordell
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Jennifer Nordell
Treehouse Teacher
Jennifer Nordell
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Jennifer Nordell
Treehouse Teacher

Hi there, jaesonshin! No, it's not incorrect. Remember, that you're counting the number of platforms listed in that table. And there are only two platforms listed. There is only "NULL" and "Xbox One". Thus, the answer should be two. If you were counting the names of the games then it would be 4.

Hope this helps! :sparkles:

jaesonshin
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jaesonshin
Python Development Techdegree Graduate 9,939 Points
jaesonshin
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jaesonshin
Python Development Techdegree Graduate 9,939 Points

Oh.. yes. COUNT() does not count NULL.

Thank you, Jennifer!!

Jaeson

Jennifer Nordell
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Jennifer Nordell
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Jennifer Nordell
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Jennifer Nordell
Treehouse Teacher

jaesonshin That's exactly correct! It does not count NULL so in this case, you get a result of 2 because it counts "Xbox One" twice. However, had you done COUNT(DISTINCT(platform)) you would get a result of 1 because NULL doesn't count at all and the "Xbox One" is repeated :smiley: