This calls for a LEFT JOIN which will select everything fr ...
左连接: var LeftJoin from t in l join t in l on t .ID equals t .ID into Joinedt from t in Joinedt .DefaultIfEmpty select new Name t .Name,Age t .Age 右连接: var RightJoin from t in l join t in l on t .ID e ...
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This calls for a LEFT JOIN which will select everything fr ...
This calls for a LEFT JOIN which will select everything ...
--一本错误的记录 insert into Book values('错误时怎样练成的',111) --左连接 select s.name,b.name from student as s left join Book as b on s.id ...
sql中的连接查询有inner join(内连接)、left join(左连接)、right join(右连接)、full join(全连接)四种方式,它们之间其实并没有太大区别,仅仅是查询出来的结果有所不同。例如我们有两张表: Orders表通过外键Id_P和Persons表进行关联 ...
1、左连接: var LeftJoin = from emp in ListOfEmployeesjoin dept in ListOfDepartmenton emp.DeptID equals dept.ID into JoinedEmpDeptfrom dept ...
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1、左连接:var LeftJoin = from emp in ListOfEmployeesjoin dept in ListOfDepartmenton emp.DeptID equals dept.ID into JoinedEmpDeptfrom dept ...
linq中的join是inner join内连接,就是当两个表中有一个表对应的数据没有的时候那个关联就不成立。 比如表A B的数据如下 的结果是 {1,1} {2,2} {4,4} 因为3在B表中不存在,所以连接失败,不返回,但是当我们需要返回一个{3, null ...