need help with Triggers

Hi All -

Can you please share your thoughts and help me ?

1. I have 4 ( T1, T2 , T3, T4 ) tables where I have the data from
a transactional system

2. I have created one more table D1 to denormalize the data from
the 4 tables ( T1, T2 , T3, T4 )

3. I have created function that returns trigger (TGR_1) .

4. I have create one trigger ( TGR_1) after insert or update on T1
& T2.

5. Now when I insert data from the application, the save function
will write data to T1 & T2.

6. The problem is the table D1 gets 2 rows, One with correct data
and the other is Blank row. I am not able to understand why I am getting a
blank row.

Any thoughts on this? Appreciate your help

Regards