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Can there be a relation without primary key?
Every table can have (but does not have to have) a primary key. The column or columns defined as the primary key ensure uniqueness in the table; no two rows can have the same key. The primary key of one table may also help to identify records in other tables, and be part of the second table’s primary key.
Can we use Unique key as foreign key?
Yes, why not. It is possible to reference a UNIQUE constraint in a FOREIGN KEY . You could have a Primary key and an Unique key, and you would like to validate both. Yes, you can reference a column (or columns) governed by either a primary key constraint or a unique constraint.
Is a Unique key?
A unique key is a set of one or more than one fields/columns of a table that uniquely identify a record in a database table. The unique key and primary key both provide a guarantee for uniqueness for a column or a set of columns.
How do you create a relationship to a non primary key in?
Is there any way I can get the cascade update/delete feature without changing the users table so that UserName is the primary key and not UserID? Create a unique index or unique constraint on UserName then you can reference it in a FK constraint fine. is incorrect.
How to define a table without a primary key?
If you want to keep your current design – which I suppose has Work (workName) as primary key and SubWork (workName, subWorkName) as a potential primary or unique key, you can define the Activity table like this (I also changed slightly the column names):
Can a table relationship be created in a data model?
In a Data Model, you cannot create a table relationship if the key is a composite key. You’re also restricted to creating one-to-one and one-to-many relationships. Other relationship types are not supported.
How to create a one to many relationship in hibernate?
That being said, I have the need to create a one-to-many, bi-directional relationship in Hibernate (4.2.1) which involves no primary keys (only a unique key on the “parent” side of the relationship) and no join tables. The foreign key representing this relationship is a backpointer from the “child” to the “parent” (see below).