One parent record with 3 possible child records

Hi,

I have one table that can have relations to only 1 of 3 possible tables.
For example: tblMain*,* tblOne, tblTwo and tblThree.

I will always have 1 record in tblMain but each record in this table will
be related to one record in tblOne OR one record in tblTwo OR one record in
tblThree.

The relation between tblMain and tblOne is 1:1.
The relation between tblMain and tblTwo is 1:1.
The relation between tblMain and tblThree is 1:1.

Is it better to set tblMain as parent or child?

This can be seen as if tblOne, tblTwo and tblThree
extend tblMain depending on a specific criteria.

Let's say that tableMain has a string field called "type" with the
following possible values: "residential", "industrial" and "energy".

I will always insert a record in tblMain but:
* If type is "residential" then a record in tblOne is created and it is
associated to tblMain,
* If type is "industrial" a record in tblTwo is created and it is
associated to tblMain
* If type is "energy" a record in tblThree is created and it is associated
to tblMain.

I am not sure how to design a case like this. I will very much appreciate
your feedback.

Best regards,
Jorge Maldonado