如何使用一个表SQL优化多选比较/连接

Question

我必须在3个条件下加入员工3次。我是否可以在3个条件下加入员工一次？

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

没有。你已经做的是正确的。