18

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).

1
  • 2
    Interesting question, I've come across these in some vendor databases, usually "settings" tables
    – Ben Brocka
    Dec 13, 2011 at 20:43

1 Answer 1

17

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

2
  • 12
    +1 A colleague suggested this moniker, too. (He also suggested "highlander table," which has a certain charm.)
    – pilcrow
    Dec 13, 2011 at 20:02
  • 3
    That's a singleton table, too.
    – miracle173
    Sep 2, 2014 at 16:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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