Question

Given:

----------------------------------
      vin     | driver | is_owner
--------------+--------+----------
 231431cxzv87 | bob    | true
 231431cxzv87 | jeff   | false
 231431cxzv87 | greg   | false
 32342klj234s | jeff   | true

Is there a way to add a constraint so that there is only one owner per vin?

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Edit: I found this question.
Is adding a partial unique index meant to suit this purpose?

Answer 1

Yes partial index is your choice.

create unique index unique__vin on table (vin) where is_owner;

Here index covers only rows where is_owner is true and withing this rows vin should be unique.