如何优化多选择比较/只有一个表的SQL

Question

我必须在3个条件参加职工3次加入。我可以在3种情况下加入一次员工吗？

select 
referType = resAffType, 

referName = (case when resAffType = 0 then e.empFirstName + ' ' + e.empLastName 

when resAffType = 1 then affFirstName + ' ' + affLastName 

else NULL end), 

bookName = e3.empFirstName + ' ' + e3.empLastName, 

AssignToName = e2.empFirstName + ' ' + e2.empLastName, 

from 

Reservation r 

left join ClubTable c on r.TableISN = c.TableISN 

left join Affiliate a on r.AffiliateISN = a.AffiliateISN -- r.aff maybe in table aff 

left join Employee e on r.AffiliateISN = e.EmployeeISN -- r.aff maybe in table emp 

left join Employee e2 on r.EmployeeISN = e2.EmployeeISN -- assignedby emp 

inner join Employee e3 on r.EmployeeISN = e3.EmployeeISN -- bookedby emp 

Answer 1

不，你已经在做的是正确的。