How do i add SUM with multiple WHERE condition? - mysql

Question

I am currently facing an issue with multiple WHERE condition
I am trying to do this condition.
SUM(IF SUM(B.answer) is lesser than 5),
SUM(IF SUM(B.answer) is between 6-10),
SUM(IF SUM(B.answer) is between 11-15),
SUM(IF SUM(B.answer) is greater than 16)
GROUP BY A.schlvl
Expecting a result like this:
Hope someone get the idea of my explanation
SELECT DISTINCT A.schlvl AS school, COUNT(DISTINCT(A.name)) AS NoOfChild, CASE WHEN SUM(B.answer)<5 THEN SUM(B.answer) END FROM child AS A INNER JOIN question AS B ON A.child_id = B.child_id
WHERE SUM(B.answer) IN (<5,>=6 && <=10,>=11 && <=15,>=16)
GROUP BY A.schlvl

Answer 1

Instead of using SUM inside a CASE WHEN, what you can do is SUM the CASE WHEN.
In this case however, when looking at the screenshot of the expected result?
I think it needs COUNT's instead.
Example:
SELECT
A.schlvl AS [School Level],
COUNT(DISTINCT(A.name)) AS [Total No. Of Children],
COUNT(DISTINCT CASE WHEN B.sum_answer <= 5 THEN A.name END) AS [le 5],
COUNT(DISTINCT CASE WHEN B.sum_answer between 6 and 10 THEN A.name END) AS [6 to 10],
COUNT(DISTINCT CASE WHEN B.sum_answer between 11 and 15 THEN A.name END) AS [11 to 15],
COUNT(DISTINCT CASE WHEN B.sum_answer >= 16 THEN A.name END) AS [ge 16]
FROM child AS A
LEFT JOIN
(
SELECT child_id, SUM(answer) AS sum_answer
FROM question
GROUP BY child_id
) AS B ON A.child_id = B.child_id
GROUP BY A.schlvl
Also, if a limit on an aggregation (f.e. SUM, COUNT) is needed, then one would do that in the HAVING clause.
I currently think it's not needed here.
Since getting the ranges of <=5 or between 6 and 15 or >=16 is hardly a limit. You need them all?

Answer 2

if you need a filter on aggregated result you must use having and not where
and you should use a valid or clause not a in clause with range
SELECT DISTINCT A.schlvl AS school
, COUNT(DISTINCT(A.name)) AS NoOfChild
, CASE WHEN SUM(B.answer)<5 THEN SUM(B.answer) END
FROM child AS A
INNER JOIN question AS B ON A.child_id = B.child_id
HAVING SUM(B.answer) IN (<5,>=6 && <=10,>=11 && <=15,>=16)
HAVING SUM(B.answer) < 5
OR (SUM(B.answer) >=6 AND SUM(B.answer) <=10)
OR (SUM(B.answer) >=11 AND SUM(B.answer) <=15)
OR (SUM(B.answer) >=16)
GROUP BY A.schlvl