Are there fundamental differences between network model vs hierarchical vs relational?

Question

Database

In what cases, it is necessary to use specific types of data models in real projects?
If I've always heard that applications are built on relational data models, then what are the rest for?

Answer 1

for everything
when here is a paying customer with a painful whip
here is soap
and here is a place for bricks
then they spin in a frying pan and look for options ruhighload.com
and until that time - an abstract or buy or copy from Wikipedia