How to store matrix ratio data in database?

Question

Database

Good afternoon, colleagues! I broke my head, I can not find the right solution:
How to store data in the database, which are matrix related to each other? For example, there are three destinations - A, B and C. Distance a-b = 100, a-c = 200, b-c = 250. It follows that the route b-a = a-b and so on. How to store such information correctly so as not to duplicate records, and when requesting a-b/b-a route, refer to the same object?

Answer 1

from
to
length
no duplication - the duty of business logic
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