[TYPO3-english] Remove child record when parents record deleted from backend

[Ngeth Chanthorn]

Dear TYPO3 Developer,

I am Ngeth Chanthorn from Cambodia, I have one problem that want to ask 
you. I want to remove child record when parents record was deleted from 
backend.

Example:
I have two tables product, and category
when I delete product, category which related to this product also 
delete, but I delete it from backend not frontend.

I also want to check if this category use by two or more products,so it 
will not delete.

I tried to search for four hours but still could not find any solution yet.

Thank you for your time.

Best regard,

Chanthorn