同一张表上的多个连接

Question

我有以下表格：

Technician
Tech_ID,First_Name,Last_Name

 RT_QUEUE_Delta
 Tech_ID, RT_Complete` (references a `Tech_ID` in `Technician`).

我需要从RT_Queue_Delta 中的一行获取数据，其中RT_Completed = ?? 但在我的输出中我需要有与Tech_id 和RT_Completed 相关的First_Name 和Last_name。

我可以匹配一个，但我不知道如何匹配两个。我试过了：

select RTTech.First_Name as RT_First_Name,
       RTTech.Last_Name as RT_Last_Name
from Technician as RTTech 
         Join RT_Queue_Delta as RT 
         on RT.RT_Completed = RTTech.Tech_ID

Answer 1

您可以多次加入Technician 表：

select d.tech_id, t.first_name, t.last_name, 
       d.rt_completed as completed_id, 
       t2.first_name as completed_first_name, 
       t2.last_name as completed_last_name
from RT_QUEUE_Delta d
    join Technician t on d.tech_id = t.tech_id
    join Technician t2 on d.RT_Completed = t2.tech_id