I think you’re misunderstanding what ON DELETE NO ACTION means. It does not mean to suppress the foreign-key constraint. When you delete a record that is referred to by a foreign key, InnoDB has the ability to take an automatic action to rectify the situation: it can CASCADE, meaning, delete the referring record. (This would … Read more
The required side of the 1..0 relationship MemberDataSet should not have a FK to DeferredData. Instead, DeferredData‘s PK should also be a FK to MemberDataSet (known as shared primary key) public class MemberDataSet { [Key] [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)] public int Id { get; set; } public virtual DeferredData DeferredData { get; set; } } public class DeferredData … Read more
Yes. Ensures that you don’t have an orphan (entry with no parent), and depending on usage, if you define a cascading delete, when a parent is deleted, all its children will also be deleted. Disadvantage would be a slight performance hit just like any other foreign key.
as with the other admin options, you need to use __ for foreign keys e.g. search_fields = [‘id’, ‘transaction__id’]
You can’t add a NOT NULL column to a table that has more than zero rows, when the column is constrained to values that match those in the parent table, and yet has only NULL values because it’s a new, unpopulated column with no DEFAULT. The workaround is to do it in stages: add the … Read more
The error is a little cryptic, so I’m not sure if this is the reason you’re getting that particular error, but I do know it will cause some error, so you can start by fixing this: What you have is two one-to-many relationships to the same model on one class. That’s not a problem per … Read more
Consider the situation where the owned entity type can also be owned by another parent entity type. Do you put foreign key references in the owned table to both parent tables? What if you have three parent types? It just doesn’t scale to large designs. A join-table decouples the join, so that the owned table … Read more
Add FOREIGN KEY (sale_id) REFERENCES Sale(sale_id) to each foreign table: CREATE TABLE Sale( sale_id CHAR(40), PRIMARY KEY(sale_id), discount DOUBLE, type VARCHAR(255), price DOUBLE ) ENGINE=INNODB; CREATE TABLE Normal_Sale( sale_id CHAR(40), PRIMARY KEY(sale_id), FOREIGN KEY (sale_id) REFERENCES Sale(sale_id) ) ENGINE=INNODB; CREATE TABLE Special_Sale( sale_id CHAR(40), PRIMARY KEY(sale_id), FOREIGN KEY (sale_id) REFERENCES Sale(sale_id) ) ENGINE=INNODB; Just make … Read more
By default, a ModelAdmin will only let you manage the model “itself”, not related models. In order to edit the related Unit model, you need to define an “InlineModelAdmin” – such as admin.TabularInline – and attach it to your CustomerAdmin. https://docs.djangoproject.com/en/dev/ref/contrib/admin/#inlinemodeladmin-objects For example, in your admin.py: from django.contrib import admin from models import Customer, Unit … Read more