Create a One-to-Many Relationship - OutSystems
In systems analysis, a one-to-many relationship is a type of cardinality that refers to the A book can have many pages, but a page can only be in one book. In a relational database, a one-to-many relationship exists when one row in table A may be. How to create one-to-many relationships between entities in OutSystems. In OutSystems, to create a one-to-many relationship between two entities, do the following: We have an application called GoOutWeb, that enables users to create. Now, we will seed the transactions table. So go to the terminal and hit the following command.
This field must have the same data type as the primary key it will refer to the primary key of Customer in this example. You can choose any name for the field. The name of a foreign key field doesn't have to be the same as the primary key field it refers to, but it is allowed. Select the Database Tools tab on the ribbon and then click the Relationships button.
This will open the Access relationships screen.
Access will ask you which tables you want to show on the relationship screen. Select the two tables you want to create the one-to-many relationship for and click Add. The tables will then appear on the relationship screen. Drag and drop the primary key of Customer to the soon to be foreign key in the Order table.
If you click Create right now you will have created a one-to-many relationship. The Enforce Referential Integrity option If you select the Enforce Referential Integrity option Access will make sure that each record in the Order table refers to an existing record in the Customer table. Selecting this option makes it impossible to create Order records thar refer to an non-existent customer. You should select Enforce Referential Integrity by default, because it protects the integrity of your data.
In case of our one-to-many example this means that if the primary key of a customer one changes, Access will automatically update the foreign keys that refer to this customer in the Order table many.
The Cascade Update Related Fields option also protects the integrity of your data as it prevents records from becoming detached from their related records. So, there can be many students in a single grade. Convention 2 Another convention is to include a collection navigation property in the principal entity as shown below.
This also results in a one-to-many relationship between the Student and Grade entities.
One-to-many (data model) - Wikipedia
This example produces the same result in the database as convention 1. Convention 3 Including navigation properties at both ends will also result in a one-to-many relationship, as shown below. Convention 4 A fully defined relationship at both ends will create a one-to-many relationship, as shown below.
This will create a one-to-many relationship with the NotNull foreign key column in the Students table, as shown below.
If the data type of GradeId is nullable integer, then it will create a null foreign key. However, you may configure relationships using Fluent API at one place to make it more maintainable.
Consider the following Student and Grade entity classes. First, we need to start configuring with any one entity class.
Configure One-to-Many Relationships in EF 6
CurrentGrade specifies that the Student entity has required the CurrentGrade property. This will create a NotNull foreign key column in the DB. Now, it's time to configure the other end of the relationship - the Grade entity. Students specifies that the Grade entity class includes many Student entities.
Here, many infers the ICollection type property.