The 1-0..1 relation in your database is directly visible. It is built between Course and OnlineCourse tables where Course is principal in relation (1) and OnlineCourse is dependent with FK configured on CourseID. FK is also PK of the OnlineCourse = it must be unique and because of that it is 0..1. Database “always” uses … Read more
Hibernate uses a strategy called inspection, which is basically this: when an object is loaded from the database a snapshot of it is kept in memory. When the session is flushed Hibernate compares the stored snapshot with the current state. If they differ the object is marked as dirty and a suitable SQL command is … Read more
Let’s start with definitions and examples of each of the concepts: Total and partial participation: Total participation (indicated by a double or thick association line) means that all the entities in an entity set must participate in the relationship. Partial participation (indicated by a single thin line) means that there can be entities in the … Read more
Associative entities are used when you need a relationship to be involved in a relationship. For example: For a normal many-to-many relationship between Student and Course, we would use just a diamond. However, if we want to associate Enrollment with Teacher, we can turn Enrollment into an associative entity. Phyiscally, our database looks like this: … Read more
Create a diagram for existing database schema or its subset as follows: Click File → Data Modeler → Import → Data Dictionary. Select a DB connection (add one if none). Click Next. Check one or more schema names. Click Next. Check one or more objects to import. Click Next. Click Finish. The ERD is displayed. … Read more
@ManyToMany to self is rather confusing because the way you’d normally model this differs from the “Hibernate” way. Your problem is you’re missing another collection. Think of it this way – if you’re mapping “author”https://stackoverflow.com/”book” as many-to-many, you need “authors” collection on Book and “books” collection on Author. In this case, your “User” entity represents … Read more
You have it backwards. The relationships in an E-R model are explicitly defined, while they are implicit in a relational model. No. Each Relational Model (RM) database base table and query result represents an application relationship. Entity-Relationship Modeling (E-RM) schemas are just a way of organizing (but under-using and under-specifying) (but with misunderstanding) relational tables … Read more
By changing pocos to: public class Order { public int OrderId { get; set; } public virtual Quotation Quotation { get; set; } } public class Quotation { public int QuotationId { get; set; } public virtual Order Order { get; set; } } and using these mapping files: public class OrderMap : EntityTypeConfiguration<Order> { … Read more
— Disable the constraints on a table called tableName: ALTER TABLE tableName NOCHECK CONSTRAINT ALL — Re-enable the constraints on a table called tableName: ALTER TABLE tableName WITH CHECK CHECK CONSTRAINT ALL ——————————————————— — Disable constraints for all tables in the database: EXEC sp_msforeachtable ‘ALTER TABLE ? NOCHECK CONSTRAINT ALL’ — Re-enable constraints for all … Read more
Make a separate set of /memberships/ resources. REST is about making evolvable systems if nothing else. At this moment, you may only care that a given player is on a given team, but at some point in the future, you will want to annotate that relationship with more data: how long they’ve been on that … Read more