https://docs.snowflake.com/en/sql-reference/constraints-over...
Note Snowflake supports defining and maintaining constraints, but does not enforce them, except for NOT NULL constraints, which are always enforced.
I don't understand what it means (and that page doesn't explain) for a 'constraint' not to be enforced? Do you somehow get some sort of warning, but not an error, i.e. the insert/update is allowed to work, everything proceeds as normal, but it's there to check on and correct if you want?
As in, you can have a sort of 'link' to another table, that not only mignt be null, but might be a value which doesn't exist over there?
What does the 'support' add over just having a column in which you tell yourself (but not your DBMS) you're storing values which correspond to keys in another table?
(You can take it further - s/keys/values in a column/ - many to one relationships without an intermediary table! Amazing! ...more 'NoSQL' than I care to go I think, for almost anything.)