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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?
Edit: I found this question.
Is adding a partial unique index meant to suit this purpose?
842
To find the name of a constraint in PostgreSQL, use the view pg_constraint in the pg_catalog schema. Join the view pg_catalog. pg_constraint with the view pg_class ( JOIN pg_class t ON t. oid = c.
What is PostgreSQL Unique key Constraint? In PostgreSQL, the UNIQUE CONSTRAINT is used to maintain the individuality of the values that we store into a field or a column of the table. It is compatible with a group of column constraints or column constraints and a table constraint.
A partial index is an index built over a subset of a table; the subset is defined by a conditional expression (called the predicate of the partial index). The index contains entries only for those table rows that satisfy the predicate.
PostgreSQL automatically creates a unique index when a unique constraint or primary key is defined for a table. The index covers the columns that make up the primary key or unique constraint (a multicolumn index, if appropriate), and is the mechanism that enforces the constraint.
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.
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