Is there a specific term to describe a relation with a cardinality of one?

I'm thinking particularly of RDBMS "special" one-row tables, for example, DUAL (Oracle), SYSIBM.SYSDUMMY1 (DB2, Derby) and RDB$DATABASE (Interbase, Firebird).

  • 2
    Interesting question, I've come across these in some vendor databases, usually "settings" tables
    – Ben Brocka
    Dec 13 '11 at 20:43

Singleton Table. In relational terms it is a relation with primary key ∅ (the empty set).

  • 12
    +1 A colleague suggested this moniker, too. (He also suggested "highlander table," which has a certain charm.)
    – pilcrow
    Dec 13 '11 at 20:02
  • 3
    That's a singleton table, too.
    – miracle173
    Sep 2 '14 at 16:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.