LINQ to SQL 多表左外连接 [英] LINQ to SQL multiple tables left outer join

问题描述

我在 SQL 中有这个查询，我希望它使用 实体框架在 LINQ 中实现它，但是如何应用多个表的左外连接?

I have this query in SQL, and I want it to implement it in LINQ using Entity Framework, but how can I apply multiple tables left outer joins?

SELECT d.bookingid,
       d.labid,
       d.processid,
       p.prid,
       p.prno,
       d.DestinationBranchID,
       d.SendStatus
FROM   dc_tpatient_bookingd d
       LEFT OUTER JOIN dc_tpatient_bookingm m ON d.bookingid = m.bookingid
       LEFT OUTER JOIN dc_tpatient p ON p.prid = m.prid
       LEFT OUTER JOIN dc_tp_test t ON d.testid = t.testid
       LEFT OUTER JOIN dc_tp_groupm gm ON t.groupid = gm.groupid
       LEFT OUTER JOIN dc_tpanel pn ON m.panelid = pn.panelid
       LEFT OUTER JOIN dc_tp_organization og ON og.orgid = m.clientid
       LEFT OUTER JOIN dc_tp_ward w ON w.wardid = m.wardid
       LEFT OUTER JOIN dc_tp_branch tb ON tb.BranchID = m.BranchID
WHERE  d.processid = 6
       AND ( ( m.branchId = 1
               AND d.DestinationBranchID = 0 )
              OR ( d.DestinationBranchID = 1
                   AND d.sendstatus = 'R' ) )
       AND d.testid IN (SELECT testid
                        FROM   dc_tp_test
                        WHERE  subdepartmentid = 13)
       AND date_format(m.enteredon, '%Y/%m/%d') BETWEEN '2013/06/15' AND '2013/06/15'
GROUP  BY m.bookingid
ORDER  BY d.priority DESC,
       m.bookingid ASC

推荐答案

以下是使用 LINQ 实现左外连接的方法.您应该使用 GroupJoin(join...into 语法):

Here is how left outer joins are implemented with LINQ. You should use GroupJoin (join...into syntax):

from d in context.dc_tpatient_bookingd
join bookingm in context.dc_tpatient_bookingm
     on d.bookingid equals bookingm.bookingid into bookingmGroup
from m in bookingmGroup.DefaultIfEmpty()
join patient in dc_tpatient
     on m.prid equals patient.prid into patientGroup
from p in patientGroup.DefaultIfEmpty()
// ... other joins here
where d.processid == 6 &&
      ((m.branchId == 1 && d.DestinationBranchID == 0) ||
       (d.DestinationBranchID == 1 && d.sendstatus == "R"))
// ... other conditions here
orderby d.priority descending, m.bookingid
select new {
   d.bookingid,
   d.labid,
   d.processid,
   p.prid,
   p.prno,
   m.bookingid // need for grouping
} into x
group x by x.bookingid into g
select g

这个查询连接了三个表.你可以用同样的方式连接其余的表.

This query joins three tables. You can join the rest of the tables the same way.

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