select
STDDEV(b.sectionscore) s,--------------- here is the sample standard deviation not all data
STDDEV(b.sectionscore) s,--------------- here is the sample standard deviation not all data
STDDEV_POP(b.sectionscore) s,---------------This is the standard deviation of all data
from subjectregister a
left join subjectsectionscore b
on a.sid = b.subjectregistersid
left join subjectsection c
on b.sectionsid = c.sid
where a.score != '0'
and a.score IS NOT null
and a.subjectcode != 'F'
and a.subjectcode != 'S'
AND