使用 EF 从数据库中查询此查询是否正确？答案

【问题标题】：Is this query from database using EF correct?使用 EF 从数据库中查询此查询是否正确？
【发布时间】：2015-10-02 07:48:27
【问题描述】：

请问这是否是使用 EF 删除整个数据库表的正确方法？ Department 表使用 DepartmentID 连接 Facility， Facility 表使用 FacilityID 连接 Facility Reservation，我需要从 Facility Reservation 表中删除所有记录。有人可以指导我并告诉我这是否正确？谢谢！

    db.Database.ExecuteSqlCommand(
                    "DELETE FacilityReservation FROM Department INNER JOIN Facility ON Department.DepartmentID = Facility.DepartmentID " +
                        "INNER JOIN FacilityReservation ON Facility.FacilityID = FacilityReservation.FacilityID WHERE Department.DepartmentID =" + departmentID);

【问题讨论】：

标签： c# mysql sql entity-framework

【解决方案1】：

不，当然不是，你需要一个 DELETE FROM ，当你进行连接时，你需要另一个“FROM

”。

你可能想要这个：

DELETE FROM FacilityReservation 

INNER JOIN Facility 
    ON Facility.FacilityID = FacilityReservation.FacilityID 

INNER JOIN Department 
    ON Department.DepartmentID = Facility.DepartmentID 

WHERE Department.DepartmentID = @departmentID;

【讨论】：

【解决方案2】：

从您的 SQL 语句看来，DepartmentID 似乎可以从您的 Facility 表中检索到。因此，您的 SQL 语句可能相当简单，例如：

DELETE a
FROM FacilityReservation a
INNER JOIN Facility b ON a.FacilityID = b.FacilityID
WHERE b.DepartmentID = @departmentID

See SQL Fiddle here.

【讨论】：