Hibernate recursive many-to-many association with the same entity

@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

is optionality (mandatory, optional) and participation (total, partial) are same?

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

What is the difference between an entity relationship model and a relational model?

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

Implementing Zero Or One to Zero Or One relationship in EF Code first by Fluent API

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

Turn off constraints temporarily (MS SQL)

— 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

How are super- and subtype relationships in ER diagrams represented as tables?

ER Notation There are several ER notations. I’m not familiar with the one you are using, but it’s clear enough you are trying to represent a subtype (aka. inheritance, category, subclass, generalization hierarchy…). This is the relational cousin of the OOP inheritance. When doing subtyping, you are generally concerned with the following design decisions: Abstract … Read more