INSERT語句衝突與我的VB.net外鍵約束

Question

所以我工作在我的項目，然後我試圖插入一些值是外鍵

INSERT語句衝突與外鍵約束條件 「SCHEDFK4」。衝突發生在數據庫「EnrollmentDatabase」中， 表「dbo.tblSubject」列'Subject_ID'。

這裏是我的SQL實體

CREATE TABLE tblGradeLevel 
(
    Grade_ID VARCHAR (5) NOT NULL, 
    Grade_Name VARCHAR (20) NULL, 
    PRIMARY KEY (Grade_ID) 
) 

CREATE TABLE tblSubject 
(
    Subject_ID VARCHAR (5)NOT NULL, 
    Subject_Name VARCHAR (20) NOT NULL, 
    Subject_Desc VARCHAR (20) NOT NULL, 
    Grade_Name VARCHAR (5) NOT NULL, 
    PRIMARY KEY (Subject_ID), 
    CONSTRAINT SUBFK1 FOREIGN KEY (Grade_ID) 
     REFERENCES tblGradeLevel (Grade_ID) 
) 

CREATE TABLE tblSchedule 
(
    Subject_Schedule_ID VARCHAR (5)NOT NULL, 
    Section_ID VARCHAR (5)NOT NULL, 
    Teacher_ID VARCHAR (5)NOT NULL, 
    Time_In VARCHAR (20)NOT NULL, 
    Time_Out VARCHAR (20)NOT NULL, 
    Subject_ID VARCHAR (5)NOT NULL, 
    Grade_ID VARCHAR (5)NOT NULL, 

    PRIMARY KEY (Subject_Schedule_ID), 
    CONSTRAINT SCHEDFK1 FOREIGN KEY (Student_ID) 
     REFERENCES tblStudent_Information (Student_ID), 
    CONSTRAINT SCHEDFK2 FOREIGN KEY (Section_ID) 
     REFERENCES tblSection (Section_ID), 
    CONSTRAINT SCHEDFK3 FOREIGN KEY (Teacher_ID) 
     REFERENCES tblTeacher (Teacher_ID), 
    CONSTRAINT SCHEDFK4 FOREIGN KEY (Subject_ID) 
     REFERENCES tblSubject (Subject_ID), 
    CONSTRAINT SCHEDFK5 FOREIGN KEY (Grade_ID) 
     REFERENCES tblGradeLevel (Grade_ID) 
) 

Answer 1

爲了避免這種錯誤的發生，請確保您插入引用另一個表中的列值在該表存在。如果該值在主表中不存在，請在對第二個表執行插入操作之前先插入該表。

爲避免此錯誤，請在insert into the [dbo].[tblsubject]表之前先插入[dbo].[tblSchedule]表。

Answer 2

從您的錯誤中很容易理解，您嘗試在tblSchedule中插入記錄，但在tblsubject表中缺少相應的Subject_ID。

你有兩個選擇來解決這個問題。

1. 降的外鍵約束。
2. 插入tblsubject需要參考tblSchedule表中的條目。

您可以在MSDN鏈接here瞭解關於外鍵約束的更多信息。