Question

我正在尝试将第一个查询的结果排除在第二个查询的结果中。

SQL等效于此处，其中A是我当前的查询，B是旧查询。

我一直在尝试使用这个guide进行左连接，但我似乎无法弄清楚它在我的情况下应该如何工作。我只是不明白这应该如何工作（我不能让语法突出显示为快乐）。

var emp = from employee in empl
    join jc in jce on callout.job_class_code_fk equals jc.job_class_code_fk
    join av in ab on employee.employee_id_pk equals av.employee_id_fk
    join sh in sho on employee.employee_id_pk equals sh.employee_id_fk into lj
    from rnd2 in lj.DefaultIfEmpty()
    orderby employee.seniority descending
    select new
    {
      eid = employee.employee_id_pk,
      sen = employee.seniority,
      nam = employee.employee_name,
      pho = employee.phone_number,
      lje = sho == null ? sho.employee_id_fk : null //left outer join with exclusion??
    };

编辑::根据评论中的建议，我尝试了以下两种方法。虽然我不再有语法问题，但以下都没有返回任何结果，所以这里仍然有问题。

    var emp = from employee in empl
              join jc in jce on callout.job_class_code_fk equals jc.job_class_code_fk
              join av in ab on employee.employee_id_pk equals av.employee_id_fk
              join sh in sho on employee.employee_id_pk equals sh.employee_id_fk into lj
              from rnd2 in lj.DefaultIfEmpty() where sho == null
              orderby employee.seniority descending
              select new
              {
                  eid = employee.employee_id_pk,
                  sen = employee.seniority,
                  nam = employee.employee_name,
                  pho = employee.phone_number,
              };

    var emp = from employee in empl
              join jc in jce on callout.job_class_code_fk equals jc.job_class_code_fk
              join av in ab on employee.employee_id_pk equals av.employee_id_fk
              join sh in sho on employee.employee_id_pk equals sh.employee_id_fk into lj
              from rnd2 in lj.DefaultIfEmpty() where rnd2 == null
              orderby employee.seniority descending
              select new
              {
                  eid = employee.employee_id_pk,
                  sen = employee.seniority,
                  nam = employee.employee_name,
                  pho = employee.phone_number,
              };

Answer 1

好的（对我而言）最容易阅读和理解的答案最终就是这样。

创建两个列表，我要排除的列表和主列表。

他们我们运行master.Except（排除）和瞧。我们已经完成了左外连接的效果而已被排除。

这是工作代码。上面的解决方案很可能有效，因为第一个列表的组合方式存在另一个问题。

LINQ左外联接有排除

1 个答案: