2013/7/27 Alvaro Herrera <alvhe...@2ndquadrant.com> > > PostgreSQL implements unique constraints by way of unique indexes (and > it's likely that all RDBMSs do likewise). Also, the syntax to declare > unique indexes allows for more features than the unique constraints > syntax. For example, you can have a unique index that covers only > portion of the table, based on a WHERE condition (a partial unique > index). You can't do this with a constraint. > Note, partial uniqueness can be achieved by using EXCLUDE contraints also.
-- // Dmitriy.
