Newbie question about derived table structure in SQL server

Hi,

I just started learning AX 2012.

And I created a base table TabPet which has field InstanceRelationType and PetBirthDate, and a derived table TabPetDog which has field NumberOfTeeth.

And I have setup the InstanceRelationType and Extends property for these two tables.

After I inserted some sample data through X++, I went to SQL server to open the tables. only TabPet table has all the fields includes NumberOfTeeth. TabPetDog table only has some columns like DATAARIEAID, RECVERSION, RELATIONTYPE, PARTITION, RECID.

Can anyone tell me why it's like this? Is it how AX designed?

Thanks a lot,

JIm