關於「PostgreSQL UNIQUE」標籤，搜尋引擎有相關的訊息討論：

In Postgresql, force unique on combination of two columnsstackoverflow.com › questions › in-postgresql-force-uniqu...UNIQUE constraint on large VARCHARs - PostgreSQLdba.stackexchange.com › questions › unique-constraint-on...PostgreSQL: Unique Constraint With Null Values - Linke