Simple observation of Table Inheritance in 2012

In this section show Table Inheritance. A table can extend/inherit another table. Each table has the “SupportInheritance” property and the “Extends” property, which together control table inheritance. When we create new table in Ax it extends default “Common” table.  The Common Table extension cannot be seen in Extends Property. “Common” table is System table that is located at AOT/System Documentation/Tables/Common.

Here, most important question is when/where to Use Table Inheritance? We can use Table Inheritance:

1.When there is one too many or many to many relationships between two tables

2.When base table and derived table both carry different information about same item/object.

I’ll show you a simple Example that will help you to understand table inheritance in Ax 2012.

First, Create a table called “ClassTable” and immediately set property “SupportInheritance – Yes” before creating any fields.You have to create a field in BaseTable(ClassTable) called “InstanceRelationType” that must be int64 type and set on InstanceRelationType on ClassTable. Create another fields according to Figure 1.

Figure 1 – Create ClassTable

Note: If you have any field in table you cannot set “SupportInheritance- Yes”. When you trying to to set “Yes” you’ll get a error like Figure 2.

Figure  2 - Error

Now, Create second Table called “Student” and immediately set property “SupportInheritance – Yes”. And set property “Extends – ClassTable” before creating any fields. After, create another fields according to figure 3.

Figure 3 – Create Student Table

After, Open “Student” table and u will get all fields from “ClassTable” in “Student” table like figure 4.

Figure 4 - Result

Note: We cannot create record directly in base table because it’s only reference. When you insert a record into a derived table, the system automatically inserts the required base table row. When you delete a record from a base table, the system automatically deletes dependent rows from the derived table.

We can also inherit methods from base table in Ax 2012 like class.