您可以搜索所有对，并过滤在一个项目中一起工作的那些对。

SELECT DISTINCT
       e1.id as emp1, 
       e2.id as emp2
FROM Employee e1
JOIN Employee e2
  ON e1.id < e2.id
WHERE not exist ( SELECT 1
                  FROM Employee r1
                  JOIN Employee r2
                    ON r1.id < r2.id
                   AND r1.ProjectNum = r2.ProjectNum 
                   AND e1.ID = r1.ID
                   AND e2.ID = r2.ID
                )

你用 e1.id < e2.id 而不是 e1.id <> e2.id 所以你不会得到相反的一对