This calls for a LEFT JOIN which will select everything fr ...
左連接: 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 右連接: var RightJoin from t in l join t in l on t .ID e ...
2017-04-12 22:51 0 4196 推薦指數:
This calls for a LEFT JOIN which will select everything fr ...
This calls for a LEFT JOIN which will select everything ...
--一本錯誤的記錄 insert into Book values('錯誤時怎樣練成的',111) --左連接 select s.name,b.name from student as s left join Book as b on s.id ...
sql中的連接查詢有inner join(內連接)、left join(左連接)、right join(右連接)、full join(全連接)四種方式,它們之間其實並沒有太大區別,僅僅是查詢出來的結果有所不同。例如我們有兩張表: Orders表通過外鍵Id_P和Persons表進行關聯 ...
1、左連接: var LeftJoin = from emp in ListOfEmployeesjoin dept in ListOfDepartmenton emp.DeptID equals dept.ID into JoinedEmpDeptfrom dept ...
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1、左連接:var LeftJoin = from emp in ListOfEmployeesjoin dept in ListOfDepartmenton emp.DeptID equals dept.ID into JoinedEmpDeptfrom dept ...
linq中的join是inner join內連接,就是當兩個表中有一個表對應的數據沒有的時候那個關聯就不成立。 比如表A B的數據如下 的結果是 {1,1} {2,2} {4,4} 因為3在B表中不存在,所以連接失敗,不返回,但是當我們需要返回一個{3, null ...