筆記 SQL Server Relationship 以及 Entity Framework 物件的對應關係。
說明
使用 Entity Framework Tutorial 所設計的資料庫以及微軟範例資料庫 Northwind 與 Adventureworks 探討在 Database First 下，資料庫索引外鍵關聯性以及 Entity Framework 類別關聯的對應關係。
1 to 0..1 relationship
Student (1)
- StudentID (PK)
- virtual StudentAddress StudentAddress
StudentAddress (0..1)
- StudentID (PK, FK)
- virtual Student Student
只存在 1 to 0..1 不存在 1 to 1 的情況。
1 to many relationship
Standard (0..1)
- StandardId (PK)
- ICollection
Teacher
Teacher (*)
- TeacherId (PK)
- int? StandardId (FK)
- virtual Standard Standard
Standard (0..1)
- StandardId (PK)
- ICollection
Student
Student (*)
- StudentID (PK)
- int? StandardId (FK)
- virtual Standard Standard
Teacher (0..1)
- TeacherId (PK)
- ICollection
Course
Course
- CourseId (PK)
- int? TeacherId (FK)
- virtual Teacher Teacher
只存在 0..1 to many 的情況，不存在 1 to many 的情況，如果有，是來自於 many to many 的衍生料表與兩端的存在。
many to many relationship
Course
- CourseId (PK)
- ICollection
Student
Student (*)
- StudentID (PK)
- ICollection
Course
StudentClass (Table but not Class)
- CourseId (PK)
- StudentID (PK)
- StudentCourseCourseId to Course.CourseId (FK)
- StudentCourseStudentId to Student.StudentId (FK)