私は3つの状況を特定しました。
- 登録のない学生。
- 登録はあるが成績がない学生。
- 登録と成績を持つ学生。
登録テーブルには、GPAを計算するトリガーがあります。学生に成績がある場合は、GPAテーブルにエントリを更新または挿入します。成績なし、GPAテーブルエントリなし。
登録のない生徒を削除できます（＃1）。登録と成績（上記の＃3）を持つ学生を削除できます。しかし、登録はあるが成績がない学生は削除できません（＃2）。参照制約違反が発生します。
DELETEステートメントがREFERENCE制約「FK_dbo.GPA_dbo.Student_StudentID」と競合しました。データベース ""、テーブル "dbo.GPA"、列 'StudentID'で競合が発生しました。
登録がなく（GPAエントリもない）新しい生徒を削除できなかった場合、制約違反は理解できますが、その生徒を削除できます。登録がなく、成績もない（それでもGPAエントリがない）学生は削除できません。
トリガーにパッチを適用したので、次に進むことができます。これで、登録がある場合、トリガーは何があってもGPAテーブルに挿入します。しかし、私は根本的な問題を理解していません。説明をいただければ幸いです。
それが価値があるもののために：
- Visual Studio 2013 Professional。
- IISエクスプレス（VS2013の内部）。
- EntityFramework 6.1.1を使用するASP.NET Webアプリ。
- MS SQL Server 2014 Enterprise。
- GPA.Valueはnull可能です。
- Enrollment.GradeIDはnull可能です。
これはデータベースのスニペットです：
- 編集 -
テーブルはすべてEntityFrameworkによって作成され、SQL Server Management Studioを使用して作成しました。
次に、制約付きのテーブル作成ステートメントを示します。
GPA テーブル：
CREATE TABLE [dbo].[GPA](
[StudentID] [int] NOT NULL,
[Value] [float] NULL,
CONSTRAINT [PK_dbo.GPA] PRIMARY KEY CLUSTERED
(
[StudentID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,
ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
ALTER TABLE [dbo].[GPA] WITH CHECK
ADD CONSTRAINT [FK_dbo.GPA_dbo.Student_StudentID]
FOREIGN KEY([StudentID])
REFERENCES [dbo].[Student] ([ID])
ALTER TABLE [dbo].[GPA]
CHECK CONSTRAINT [FK_dbo.GPA_dbo.Student_StudentID]Enrollment テーブル：
CREATE TABLE [dbo].[Enrollment](
[EnrollmentID] [int] IDENTITY(1,1) NOT NULL,
[CourseID] [int] NOT NULL,
[StudentID] [int] NOT NULL,
[GradeID] [int] NULL,
CONSTRAINT [PK_dbo.Enrollment] PRIMARY KEY CLUSTERED
(
[EnrollmentID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,
ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
ALTER TABLE [dbo].[Enrollment] WITH CHECK
ADD CONSTRAINT [FK_dbo.Enrollment_dbo.Course_CourseID]
FOREIGN KEY([CourseID])
REFERENCES [dbo].[Course] ([CourseID])
ON DELETE CASCADE
ALTER TABLE [dbo].[Enrollment]
CHECK CONSTRAINT [FK_dbo.Enrollment_dbo.Course_CourseID]
ALTER TABLE [dbo].[Enrollment] WITH CHECK
ADD CONSTRAINT [FK_dbo.Enrollment_dbo.Grade_GradeID]
FOREIGN KEY([GradeID])
REFERENCES [dbo].[Grade] ([GradeID])
ALTER TABLE [dbo].[Enrollment]
CHECK CONSTRAINT [FK_dbo.Enrollment_dbo.Grade_GradeID]
ALTER TABLE [dbo].[Enrollment] WITH CHECK
ADD CONSTRAINT [FK_dbo.Enrollment_dbo.Student_StudentID]
FOREIGN KEY([StudentID])
REFERENCES [dbo].[Student] ([ID])
ON DELETE CASCADE
ALTER TABLE [dbo].[Enrollment]
CHECK CONSTRAINT [FK_dbo.Enrollment_dbo.Student_StudentID]Student テーブル：
CREATE TABLE [dbo].[Student](
[ID] [int] IDENTITY(1,1) NOT NULL,
[EnrollmentDate] [datetime] NOT NULL,
[LastName] [nvarchar](50) NOT NULL,
[FirstName] [nvarchar](50) NOT NULL,
CONSTRAINT [PK_dbo.Student] PRIMARY KEY CLUSTERED
(
[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,
ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]ここにトリガーがあります：
CREATE TRIGGER UpdateGPAFromUpdateDelete
ON Enrollment
AFTER UPDATE, DELETE AS
BEGIN
DECLARE @UpdatedStudentID AS int
SELECT @UpdatedStudentID = StudentID FROM DELETED
EXEC MergeGPA @UpdatedStudentID
END
CREATE TRIGGER UpdateGPAFromInsert
ON Enrollment
AFTER INSERT AS
--DECLARE @InsertedGradeID AS int
--SELECT @InsertedGradeID = GradeID FROM INSERTED
--IF @InsertedGradeID IS NOT NULL
BEGIN
DECLARE @InsertedStudentID AS int
SELECT @InsertedStudentID = StudentID FROM INSERTED
EXEC MergeGPA @InsertedStudentID
END先に進むパッチは、AFTER INSERTトリガー内のそれらの行をコメント化することでした。
これがストアドプロシージャです。
CREATE PROCEDURE MergeGPA @StudentID int AS
MERGE GPA AS TARGET
USING (SELECT @StudentID) as SOURCE (StudentID)
ON (TARGET.StudentID = SOURCE.StudentID)
WHEN MATCHED THEN
UPDATE
SET Value = (SELECT Value FROM GetGPA(@StudentID))
WHEN NOT MATCHED THEN
INSERT (StudentID, Value)
VALUES(SOURCE.StudentID, (SELECT Value FROM GetGPA(@StudentID)));これがデータベース関数です：
CREATE FUNCTION GetGPA (@StudentID int)
RETURNS TABLE
AS RETURN
SELECT ROUND(SUM (StudentTotal.TotalCredits) / SUM (StudentTotal.Credits), 2) Value
FROM (
SELECT
CAST(Credits as float) Credits
, CAST(SUM(Value * Credits) as float) TotalCredits
FROM
Enrollment e
JOIN Course c ON c.CourseID = e.CourseID
JOIN Grade g ON e.GradeID = g.GradeID
WHERE
e.StudentID = @StudentID AND
e.GradeID IS NOT NULL
GROUP BY
StudentID
, Value
, e.courseID
, Credits
) StudentTotalこれは、コントローラーの削除メソッドからのデバッグ出力です。selectステートメントは、何を削除するかを照会するメソッドです。この学生には3つの登録がありREFERENCEます。3番目の登録が削除されると、制約の問題が発生します。登録が削除されていないため、EFはトランザクションを使用していると思います。
iisexpress.exe Information: 0 : Component:SQL Database;Method:SchoolInterceptor.ReaderExecuted;Timespan:00:00:00.0004945;Properties:
Command: SELECT
[Project2].[StudentID] AS [StudentID],
[Project2].[ID] AS [ID],
[Project2].[EnrollmentDate] AS [EnrollmentDate],
[Project2].[LastName] AS [LastName],
[Project2].[FirstName] AS [FirstName],
[Project2].[Value] AS [Value],
[Project2].[C1] AS [C1],
[Project2].[EnrollmentID] AS [EnrollmentID],
[Project2].[CourseID] AS [CourseID],
[Project2].[StudentID1] AS [StudentID1],
[Project2].[GradeID] AS [GradeID]
FROM ( SELECT
[Limit1].[ID] AS [ID],
[Limit1].[EnrollmentDate] AS [EnrollmentDate],
[Limit1].[LastName] AS [LastName],
[Limit1].[FirstName] AS [FirstName],
[Limit1].[StudentID] AS [StudentID],
[Limit1].[Value] AS [Value],
[Extent3].[EnrollmentID] AS [EnrollmentID],
[Extent3].[CourseID] AS [CourseID],
[Extent3].[StudentID] AS [StudentID1],
[Extent3].[GradeID] AS [GradeID],
CASE WHEN ([Extent3].[EnrollmentID] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
FROM (SELECT TOP (2)
[Extent1].[ID] AS [ID],
[Extent1].[EnrollmentDate] AS [EnrollmentDate],
[Extent1].[LastName] AS [LastName],
[Extent1].[FirstName] AS [FirstName],
[Extent2].[StudentID] AS [StudentID],
[Extent2].[Value] AS [Value]
FROM [dbo].[Student] AS [Extent1]
LEFT OUTER JOIN [dbo].[GPA] AS [Extent2] ON [Extent1].[ID] = [Extent2].[StudentID]
WHERE [Extent1].[ID] = @p__linq__0 ) AS [Limit1]
LEFT OUTER JOIN [dbo].[Enrollment] AS [Extent3] ON [Limit1].[ID] = [Extent3].[StudentID]
) AS [Project2]
ORDER BY [Project2].[StudentID] ASC, [Project2].[ID] ASC, [Project2].[C1] ASC:
iisexpress.exe Information: 0 : Component:SQL Database;Method:SchoolInterceptor.NonQueryExecuted;Timespan:00:00:00.0012696;Properties:
Command: DELETE [dbo].[Enrollment]
WHERE ([EnrollmentID] = @0):
iisexpress.exe Information: 0 : Component:SQL Database;Method:SchoolInterceptor.NonQueryExecuted;Timespan:00:00:00.0002634;Properties:
Command: DELETE [dbo].[Enrollment]
WHERE ([EnrollmentID] = @0):
iisexpress.exe Information: 0 : Component:SQL Database;Method:SchoolInterceptor.NonQueryExecuted;Timespan:00:00:00.0002512;Properties:
Command: DELETE [dbo].[Enrollment]
WHERE ([EnrollmentID] = @0):
iisexpress.exe Error: 0 : Error executing command: DELETE [dbo].[Student]
WHERE ([ID] = @0) Exception: System.Data.SqlClient.SqlException (0x80131904): The DELETE statement conflicted with the REFERENCE constraint "FK_dbo.GPA_dbo.Student_StudentID". The conflict occurred in database "<databasename>", table "dbo.GPA", column 'StudentID'.
The statement has been terminated.