mysql count vs sum

atem answered on June 16, 2020 Popularity 8/10 Helpfulness 5/10

answer mysql count vs sum

mysql count vs sum

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+----+------+
| id | vote |
+----+------+
|  1 |    1 |       COUNT(vote) = 5 
|  2 |   -1 |		SUM(vote) = 1  = (-2 + 3 = 1)
|  3 |    1 |			  
|  4 |   -1 |	#Sum is doing the mathematical sum, whereas count simply 
|  5 |    1 |	#counts any value as 1 regardless of what data type.
+----+------+

/**
The first query returns the number of times the condition is true, because true is 1 and false is 0.
The second query returns the complete record count because count() does not care about the content inside it, as long as the content is NOT NULL. Because count(1) and count(0) are still values and both get counted.
To get the correct return value for the second query you would have to make the result of the condition be null (instead of 0) to not being counted. Like this:
*/
SELECT COUNT(case when USER_NAME = 'JoeBlow' then 'no matter what' else NULL end) 
from your_table

Popularity 8/10 Helpfulness 5/10 Language sql

Source: stackoverflow.com

Tags: count mysql sql sum

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