Seosed

select*from Employees
select * from Department

Seosed – join
füüsiline seos – on lisatud Foreigenkey (constraint – piirang näiteks kontrollida diagrammi
loogolone seos – kui õigesti kirjutada select joiniga

--JOIN
Select * from Employees join Department
on Employees.DepartmentId=Department.Id

--kirjutamine lihtsamaks
Select e.Name, e.Salary, d.DepartmentName
from Employees e join Department d 
on e.DepartmentId=d.Id

inner join sama nagu lihtne join
näitab kõik department, kus on olemas väärtus

Select e.Name, e.Salary, d.DepartmentName
from Employees e Inner join Department d 
on e.DepartmentId=d.Id

left Join
näitab kõike DepartmentName (Null väärtused)

Select e.Name, e.Salary, d.DepartmentName
from Employees e left join Department d 
on e.DepartmentId=d.Id

--right Join
Select e.Name, e.Salary, d.DepartmentName
from Employees e right join Department d 
on e.DepartmentId=d.Id

--outer join = full outer join
--näitab kõik`väärtused kahest tabelist
Select e.Name, e.Salary, d.DepartmentName
from Employees e Full outer join Department d 
on e.DepartmentId=d.Id

--cross join
--näitab nii, et 1.tabelis väärtused * 2.tabeli väärtused
select Name, Salary, DepartmentName
from Employees cross join Department

--Näidata ainult need isikud, kellel departmentName on Null
Select e.Name, e.Salary, d.DepartmentName
from Employees e right join Department d 
on e.DepartmentId=d.Id
where d.DepartmentName is Null;

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