Walkthrough: Creating Base and Derived Tables

Applies To: Microsoft Dynamics AX 2012 R3, Microsoft Dynamics AX 2012 R2, Microsoft Dynamics AX 2012 Feature Pack, Microsoft Dynamics AX 2012

In Microsoft Dynamics AX, a table can inherit from another table. The AOT node for each table has the Extends property which you can use to derive your table from a table that you specify. There are other table properties related to inheritance which must be assigned values in a specific sequence.

Background for this Walkthrough

The following topics provide background for this walkthrough:

• How to: Create Tables

• X++ Keywords – for the extends keyword about inheritance among classes.

• When to Use Table Inheritance

Create Two Tables

In this section you create a base table named TabPet, and you create a derived table named TabPetDog that extends the base table.

To create the TabPet base table

1. In the AOT, open the Data Dictionary node, right-click the Tables node, and then click New Table.

2. In the Properties window, enter the value TabPet for the Name property.

3. For the SupportInheritance property, open the drop-down box and select Yes.

   Warning

   If you cannot set the SupportInheritance property to Yes, it might be because you already have fields in the table. These fields must be deleted before you can set the value to Yes.

To create the TabPetDog derived table

1. Create a table named TabPetDog.

2. Set the SupportInheritance property to Yes.

Add Fields to the TabPet Base Table

In this section you add fields to the TabPet base table. The inheritance rules require that you add a field of type int64 to the base table. The system uses this field to match each row in the base table to the corresponding derived table. This is necessary because several derived tables could all extend from the same base table.

To add fields to the TabPet base table

1. Open your TabPet table node and right-click the Fields node, select New, and then click Int64.

2. On the Properties window that opens, name the Int64 field InstanceRelationType.

3. Add a Date field named PetBirthDate.

4. In the Properties window for PetBirthDate, open the drop-down box for the Mandatory field and set it to Yes.

Set More Inheritance Properties on the Tables

In this section you set properties on the two tables to establish their inheritance relationship.

The system uses a field on the TabPet base table to record the table ID of which ever derived table corresponds to each base table row. The InstanceRelationType property tells the system which field must store the table IDs. The field must be of type Int64.

The Extends property is set on the TabPetDog derived table. It is similar to the extends keyword that is used in the classDeclaration node for a derived class.

To set inheritance properties on the tables

1. In the Properties window for your TabPet base table, set the InstanceRelationType property to InstanceRelationType.

2. In the Properties window for your TabPetDog derived table, set the Extends property to TabPet.

Add Fields to the TabPetDog Derived Table

In this section you add fields to the TabPetDog derived table.

To add fields to the TabPetDog derived table

1. To your TabPetDog derived table, add an Integer field named NumberOfTeeth.

2. In the Properties window for the Number of Teeth field, set its Mandatory property to Yes.

Note

The same field name cannot be used in a derived table and its base table.

Next Steps

Inheritance between tables affects data operations such as select and delete. For a walkthrough that describes these effects, see Data Operations in X++ on Base and Derived Tables.

See also

Table Inheritance Overview

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