7. Partition By -SQL code(open)

	-- Partition By		-count(gender)보기
select FirstName, LastName, Gender, Salary
	,COUNT(Gender) over (partition by gender) as TotalGender
from [SQL Tutorial].dbo.EmployeeDemographics dem
join [SQL Tutorial].dbo.EmployeeSalary sal
	on dem.EmployeeID = sal.EmployeeID
    
    
	--Group By			-count(gender)보기 -한 row씩밖에 못한다 생각하면 됨.
					-- sticking it on one line in the select statement
select Gender, COUNT(Gender)
from [SQL Tutorial].dbo.EmployeeDemographics dem
join [SQL Tutorial].dbo.EmployeeSalary sal
	on dem.EmployeeID = sal.EmployeeID
group by Gender
	--결론 : 데이터 다 보고 싶으면 PARTITION BY, 요약해서 하나씩 한줄씩만 보려면 GROUP BY